HACK: configs/rdn2*: add workaround for ArmVirtPkg memory protection policy

A recent edk2 patch updated the memory protection policy for ArmVirtPkg:
("2997ae3873 ArmVirtPkg: make EFI_LOADER_DATA non-executable")
This removed the execute permissions from EFI_LOADER_DATA allocations by
updating the PCD PcdDxeNxMemoryProtectionPolicy from 0xC000000000007FD1
to 0xC000000000007FD5.

This change corresponds to the following change on grub:
("f82633068 efi: change heap allocation type to GRUB_EFI_LOADER_CODE")

Few distributions however may not have pulled in above mentioned grub
change and so booting these distros on platforms such as ArmVirtKvmTool
with uefi firmware that has non-executable EFI_LOADER_DATA change result
in asynchronous instruction aborts.
Add a workaround to build ArmVirtKvmTool platform by forcefully setting
PcdDxeNxMemoryProtectionPolicy to 0xC000000000007FD1.

Signed-off-by: Vivek Gautam <vivek.gautam@arm.com>
Change-Id: I2521fe42ce7e7f789c66ddac103b07d37ca6577d