dev-arm: Limit number of max PE in GICv3 to 128

dev-arm: Limit number of max PE in GICv3 to 128

This is needed since there is a problem in the memory layout of
VExpress_GEM5_V2 as it is: having 256KB pages is creating overlapping
regions when reserving space for 256 PEs.

GICv3 redistributors: 0x2c010000 - 0x30010000
PCI regions: 0x30000000 - 0x40000000

We fix this by cutting down the number of supported PEs to 128

Change-Id: I6e87f66a6150a441ccba298662b4548a4972dc40
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/18392
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>