tizenrt: Import Kconfig.runtime to TizenRT config dir (#1529)

If this file is merged in upstream,
then vanilla iotjs can integrated into TizenRT very easly
by just cloning into:

TizenRT/external/iotjs/

One other benefit is to improve cooperation model,
and avoiding downstream maintenance of iotjs (forked import).

Note that Tizen:RT's os/Kconfig.runtime will need to be updated
from "external/iotjs/Kconfig.runtime" (downstream's location)
to "external/iotjs/config/tizenrt/Kconfig.runtime" (upstream's location)
from this patch.

Relate-to: Samsung/TizenRT#1277

For the record, here is history of file in TizenRT's master branch:

  commit 09cb6a6a9cc68598dcbd9abe12fcdb44e478bb16
  Author: sunghan <sh924.chang@samsung.com>
  Date:   Fri Sep 22 21:13:24 2017 +0900

    IoT.js: modify Kconfig to be called with Runtime Environment title

    1. Split Kconfig from external's
    2. Call it from os/Kconfig.runtime to get "Runtime Environment" title
       at 1st depth of menuconfig

  commit d9d52392ab5d8411eb5a24a58e123f01aa984b5f
  Author: Philippe Coval <philippe.coval@osg.samsung.com>
  Date:   Thu Jan 4 17:11:06 2018 +0100

    iotjs: Select SPI in KConfig

    Observed issue was:

      iotjs_module_spi-tizenrt.c:23:2: \
      error: #error "\n\nTizenRT CONFIG_SPI_EXCHANGE flag required for SPI module\n\n"

    Change-Id: I8ec289c680973f7949d48b64a459524dab2083e0
    Signed-off-by: Philippe Coval <philippe.coval@osg.samsung.com>

Bug: #1529
IoT.js-DCO-1.0-Signed-off-by: Philippe Coval philippe.coval@osg.samsung.com

config/tizenrt/Kconfig.runtime

@@ -0,0 +1,34 @@
+#
+# For a description of the syntax of this configuration file,
+# see kconfig-language at https://www.kernel.org/doc/Documentation/kbuild/kconfig-language.txt
+#
+
+config ENABLE_IOTJS
+	bool "IoT.js"
+	default n
+	select SPI_EXCHANGE
+	select IOTBUS
+	select IOTBUS_GPIO
+	select IOTBUS_I2C
+	select IOTBUS_PWM
+	select IOTBUS_SPI
+	select IOTBUS_UART
+	---help---
+		Enable IoT.js framework
+
+if ENABLE_IOTJS
+
+config IOTJS_PRIORITY
+        int "IoT.js task priority"
+        default 100
+
+config IOTJS_STACKSIZE
+        int "IoT.js stack size"
+        default 32768
+
+config IOTJS_JERRY_HEAP
+        int "Jerryscript Heaplimit"
+        default 128
+
+endif #ENABLE_IOTJS
+