ArmPkg/ArmDmaLib: do not remap arbitrary memory regions as uncached

ArmPkg/ArmDmaLib: do not remap arbitrary memory regions as uncached

In the DmaMap () operation, if the region to be mapped happens to be
aligned to the Cache Writeback Granule (CWG) (whose value is typically
64 or 128 bytes and 2 KB maximum), we remap the memory as uncached.

Since remapping memory occurs at page granularity, while the buffer and the
CWG may be much smaller, there is no telling what other memory we affect
by doing this, especially since the operation is not reverted in DmaUnmap().

So remove the remapping call.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>