MdePkg/BaseSynchronizationLib: Added proper support for ARM architecture

MdePkg/BaseSynchronizationLib: Added proper support for ARM architecture

This implements the following synchronization primitives for AArch64 (GCC)
and ARM (GCC & RVCT):

InternalSyncCompareExchange32
InternalSyncCompareExchange64
InternalSyncIncrement
InternalSyncDecrement

Note: these functions are implemented using the exclusive monitor,
which implies that they can only be used after the caches (and hence
the MMU) have been enabled.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Olivier Martin <olivier.martin@arm.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@16965 6f19259b-4bc3-4df7-8a09-765794883524