ArmPlatformPkg/ArmVExpressPkg: Add build option to support VExpress A15 QEMU emulation

ArmPlatformPkg/ArmVExpressPkg: Add build option to support VExpress A15 QEMU emulation

This patch adds an EDK2_ARMVE_SUPPORT_QEMU macro that can be defined at build
time to build an image that supports QEMU.  The default build is unchanged and
builds the RTSM configuration.

QEMU only models fixed size blocks within a flash device, and the RTSM
configuration stores EFI variables in the smaller boot blocks of the
flash.  When built for QEMU the larger blocks are used that QEMU properly
emulates.

Signed-off-by: Roy Franz <roy.franz@linaro.org>
Contributed-under: TianoCore Contribution Agreement 1.0
Reviewed-By: Olivier Martin <olivier.martin@arm.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@15125 6f19259b-4bc3-4df7-8a09-765794883524