Add tire pressure unit to HMI (COVESA#501)

* Add tire pressure unit to HMI

- It needs to add tire pressure unit to HMI branch because there are three different units related with tire pressure in usual.

* Fix syntax error

- add ':' into the end of "HMI.TirePressureUnit"

* Replace allowed value strings with upper case

- Replace allowed value strings with upper case

spec/Cabin/Infotainment.vspec

@@ -134,6 +134,12 @@ HMI.TemperatureUnit:
   type: actuator
   allowed: ['C', 'F']
   description: Temperature unit used in the current HMI
+
+HMI.TirePressureUnit:
+  datatype: string
+  type: actuator
+  allowed: [‘PSI’, ‘KPA’, ’BAR’]
+  description: Tire pressure unit used in the current HMI 
 
 HMI.DayNightMode:
   datatype: string