[device]: Add a new supported device AS7312-54XS (#1821)

* Switch Vendor: Edge-core
* Switch SKU: AS7312-54XS
* ASIC Vendor: Broadcom
* Swich ASIC: Tomahawk+
* Port Configuration: 48x25G + 6x100G
* SONiC Image: SONiC-ONIE-Broadcom
Signed-off-by: polly_hsu@edge-core.com

device/accton/x86_64-accton_as7312_54xs-r0/Accton-AS7312-54XS/port_config.ini

@@ -0,0 +1,55 @@
+# name          lanes                 alias             index
+Ethernet0       41                    twentyfiveGigE1   0
+Ethernet1       42                    twentyfiveGigE2   1
+Ethernet2       43                    twentyfiveGigE3   2
+Ethernet3       44                    twentyfiveGigE4   3
+Ethernet4       49                    twentyfiveGigE5   4
+Ethernet5       50                    twentyfiveGigE6   5
+Ethernet6       51                    twentyfiveGigE7   6
+Ethernet7       52                    twentyfiveGigE8   7
+Ethernet8       53                    twentyfiveGigE9   8
+Ethernet9       54                    twentyfiveGigE10  9
+Ethernet10      55                    twentyfiveGigE11  10
+Ethernet11      56                    twentyfiveGigE12  11
+Ethernet12      65                    twentyfiveGigE13  12
+Ethernet13      66                    twentyfiveGigE14  13
+Ethernet14      67                    twentyfiveGigE15  14
+Ethernet15      68                    twentyfiveGigE16  15
+Ethernet16      33                    twentyfiveGigE17  16
+Ethernet17      34                    twentyfiveGigE18  17
+Ethernet18      35                    twentyfiveGigE19  18
+Ethernet19      36                    twentyfiveGigE20  19
+Ethernet20      37                    twentyfiveGigE21  20
+Ethernet21      38                    twentyfiveGigE22  21
+Ethernet22      39                    twentyfiveGigE23  22
+Ethernet23      40                    twentyfiveGigE24  23
+Ethernet24      69                    twentyfiveGigE25  24
+Ethernet25      70                    twentyfiveGigE26  25
+Ethernet26      71                    twentyfiveGigE27  26
+Ethernet27      72                    twentyfiveGigE28  27
+Ethernet28      81                    twentyfiveGigE29  28
+Ethernet29      82                    twentyfiveGigE30  29
+Ethernet30      83                    twentyfiveGigE31  30
+Ethernet31      84                    twentyfiveGigE32  31
+Ethernet32      85                    twentyfiveGigE33  32
+Ethernet33      86                    twentyfiveGigE34  33
+Ethernet34      87                    twentyfiveGigE35  34
+Ethernet35      88                    twentyfiveGigE36  35
+Ethernet36      97                    twentyfiveGigE37  36
+Ethernet37      98                    twentyfiveGigE38  37
+Ethernet38      99                    twentyfiveGigE39  38
+Ethernet39      100                   twentyfiveGigE40  39
+Ethernet40      101                   twentyfiveGigE41  40
+Ethernet41      102                   twentyfiveGigE42  41
+Ethernet42      103                   twentyfiveGigE43  42
+Ethernet43      104                   twentyfiveGigE44  43
+Ethernet44      105                   twentyfiveGigE45  44
+Ethernet45      106                   twentyfiveGigE46  45
+Ethernet46      107                   twentyfiveGigE47  46
+Ethernet47      108                   twentyfiveGigE48  47
+Ethernet48      5,6,7,8               hundredGigE49     48
+Ethernet52      1,2,3,4               hundredGigE50     52
+Ethernet56      109,110,111,112       hundredGigE51     56
+Ethernet60      21,22,23,24           hundredGigE52     60
+Ethernet64      9,10,11,12            hundredGigE53     64
+Ethernet68      117,118,119,120       hundredGigE54     68

device/accton/x86_64-accton_as7312_54xs-r0/Accton-AS7312-54XS/sai.profile

@@ -0,0 +1 @@
+SAI_INIT_CONFIG_FILE=/usr/share/sonic/hwsku/th-as7312-48x25G+6x100G.config.bcm