ArmPkg/BdsLib/Arm: Clean Data cache before disabling it

ArmPkg/BdsLib/Arm: Clean Data cache before disabling it

It is actually the same sequence as AArch64.
Without cleaning the data cache prior to disable the cache, the LR value
pushed on the stack when entering in ArmCleanInvalidateDataCache()
might have been overwritten by this specific cache line maintenance.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Olivier Martin <olivier.martin@arm.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16012 6f19259b-4bc3-4df7-8a09-765794883524