dev-arm: Fix setupBootloader for VExpress_GEM5_V2

dev-arm: Fix setupBootloader for VExpress_GEM5_V2

Recent changes in the setupBootloader method didn't take into account
that the VExpress_GEM5_Base class does require "loc" to be passed
to the bootloader setup method:

setupBootLoader(self, cur_sys, loc, boot_loader=None)

However VExpress_GEM5_V2_Base was just passing cur_sys and boot_loader
so that the bootloader was being passed as loc and boot_loader was
passed as None (default parameter):

super(VExpress_GEM5_V2_Base, self).setupBootLoader(
        cur_sys, boot_loader)

This patch is fixing this by removing loc from the VExpress_GEM5_Base
interface: the bootloader defaults (usinbg loc) are being set in the
derived classes (V1 and V2)

Change-Id: Ic4d4e4fd8d45a7af9207900287828119c3d7d56c
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/25583
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>