[Linaro-uefi] AARCH64 GIC updates for 64 bit

Hi,

I have added support for a future Broadcom server SOC in edk2. I have booted all the way to the console. WE have some tweaks to the fast model to model the device. Along the way one of the updates i had to make was adding support for GIC in a 64 bit memory map. The patch is along similar lines to patches that have been posted recently on the mailing list. Couple of questions

- Can this patch be submitted for review; i don't believe i will be sending the patches for our fast model based port.

- Since i am a little new to UEFI, do i actually need to modify the PCD's for other platforms in the appropriate .dec files. If platforms have GIC in the lower 32 bit, do i have to change the PCD definition to a UINT64 from a UINT32?