configs, arch-arm: Check if gic has cpu_addr attribute

configs, arch-arm: Check if gic has cpu_addr attribute

Add this check because Gicv3 does not have the cpu_addr attribute.

Test: Change VExpress_GEM5_V1() to VExpress_GEM5_V2() and run the
following command to boot Debian.

M5_PATH=$PWD/fs_files ./build/ARM/gem5.opt ./configs/example/arm/fs_bigLITTLE.py \
--dtb $PWD/fs_files/binaries/armv8_gem5_v2_1cpu.dtb \
--kernel $PWD/fs_files/binaries/vmlinux \
--disk $PWD/fs_files/disks/disk.img \
--cpu-type atomic --big-cpus 1 --little-cpus 0

Change-Id: I23595ae5238dc7cc915ab09300f91aa5e8c24fdc
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/19648
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>