Ovmf/Xen: port XenBusDxe to other architectures

This patch updates XenBusDxe to use the 16-bit compare and exchange
function that was introduced for this purpose to the
BaseSynchronizationLib. It also provides a new generic implementation
of TestAndClearBit () using the same 16-bit compare and exchange, making
this module fully architecture agnostic.

Contributed-under: TianoCore Contribution Agreement 1.0
Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Laszlo Ersek <lersek@redhat.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16975 6f19259b-4bc3-4df7-8a09-765794883524

OvmfPkg/XenBusDxe/XenBusDxe.inf

@@ -34,8 +34,6 @@
   DriverBinding.h
   ComponentName.c
   ComponentName.h
-  InterlockedCompareExchange16.c
-  InterlockedCompareExchange16.h
   GrantTable.c
   GrantTable.h
   EventChannel.c
@@ -45,14 +43,7 @@
   XenBus.c
   XenBus.h
   Helpers.c
-
-[Sources.IA32]
-  Ia32/InterlockedCompareExchange16.nasm
-  Ia32/TestAndClearBit.nasm
-
-[Sources.X64]
-  X64/InterlockedCompareExchange16.nasm
-  X64/TestAndClearBit.nasm
+  TestAndClearBit.c
 
 [LibraryClasses]
   UefiDriverEntryPoint
@@ -64,6 +55,7 @@
   DevicePathLib
   DebugLib
   XenHypercallLib
+  SynchronizationLib
 
 [Protocols]
   gEfiDriverBindingProtocolGuid