KVM: arm64: vgic-v3: Check ITS region is not above the VM IPA size

Verify that the ITS region does not extend beyond the VM-specified IPA
range (phys_size).

  base + size > phys_size AND base < phys_size

Add the missing check into vgic_its_set_attr() which is called when
setting the region.

Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Ricardo Koller <ricarkol@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211005011921.437353-5-ricarkol@google.com