ArmPkg/Include: Add ArmSvcLib header file.

ArmSvcLib header file to specify the SVC arguments structure and
function prototype to trigger an SVC call.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Achin Gupta <achin.gupta@arm.com>
Signed-off-by: Supreeth Venkatesh <supreeth.venkatesh@arm.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

ArmPkg/ArmPkg.dec

@@ -39,6 +39,7 @@
   DefaultExceptionHandlerLib|Include/Library/DefaultExceptionHandlerLib.h
   ArmDisassemblerLib|Include/Library/ArmDisassemblerLib.h
   ArmGicArchLib|Include/Library/ArmGicArchLib.h
+  ArmSvcLib|Include/Library/ArmSvcLib.h
 
 [Guids.common]
   gArmTokenSpaceGuid       = { 0xBB11ECFE, 0x820F, 0x4968, { 0xBB, 0xA6, 0xF7, 0x6A, 0xFE, 0x30, 0x25, 0x96 } }