ArmPkg: Changed Uncached System Memory from EFI_MEMORY_UC to EFI_MEMORY_WC

ArmPkg: Changed Uncached System Memory from EFI_MEMORY_UC to EFI_MEMORY_WC

EFI_MEMORY_UC is mapped to Strongly Ordered memory while EFI_MEMORY_WC is
mapped to Uncached Normal/System memory.
This change improve performance while accessing uncached regions in the
System Memory.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Eugene Cohen <eugene@hp.com>
Reviewed-by: Olivier Martin <oliviermartin@arm.com
git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@13693 6f19259b-4bc3-4df7-8a09-765794883524