ArmPkg: allow patchable PCDs for memory, FD and FV addresses

ArmPkg: allow patchable PCDs for memory, FD and FV addresses

In order to allow a runtime self relocating PrePi instance, change the
allowable PCD types for the following PCDs:

  gArmTokenSpaceGuid.PcdSystemMemoryBase
  gArmTokenSpaceGuid.PcdSystemMemorySize
  gArmTokenSpaceGuid.PcdFdBaseAddress
  gArmTokenSpaceGuid.PcdFvBaseAddress

to include PcdsPatchableInModule. This makes the build system correctly
distinguish fixed PCDs from PCDs whose value may be different from the
assigned value at compile time.

Note that this only affects platforms that explicitly mark these PCDs as
PatchableInModule in the DSC. All existing platforms that use FixedPcd
will not be affected by this change.

Contributed-under: TianoCore Contribution Agreement 1.0
Acked-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-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@16954 6f19259b-4bc3-4df7-8a09-765794883524