ArmPkg: use unified asm syntax for CLANG

ArmPkg: use unified asm syntax for CLANG

The CLANG assembler does not support the legacy, non-unified assembler syntax,
i.e., it does not support the reordering of the condition suffixes with the
increment/decrement before/after or byte/word suffixes, and it does not
recognize the 'empty descending' (ED) suffix at all. So move to the unified
syntax, and replace 'empty descending' with 'decrement after' or 'increment
before' as appropriate.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@19280 6f19259b-4bc3-4df7-8a09-765794883524