ArmPkg: split off ArmGicArchLib from ArmGicLib

ArmPkg: split off ArmGicArchLib from ArmGicLib

The current implementation of ArmGicGetSupportedArchRevision ()
that is used by all ARM platforms is entirely stateless (in order
to support being executed from flash) so it needs to interrogate
the hardware for the supported GIC revision upon each invocation.

However, this statelessness is only needed for SEC type modules;
in all other cases, we could easily determine the GIC revision once,
and store the result in a global variable.

In preparation of having separate early and normal versions, this patch
introduces the ArmGicArchLib library class and default implementation,
and moves the existing ArmGicGetSupportedArchRevision () into it.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
Tested-by: Leif Lindholm <leif.lindholm@linaro.org>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18098 6f19259b-4bc3-4df7-8a09-765794883524