In locore.S we need to configure access to the GICv3. To check if it's
available we read the id_aa64pfr0_el1 register, however we then only
check if a GICv3.0 or 4.0 is present. If the system has a GICv4.1 this
check would fail.
Move to checking if the GICV3+ is not absent so this will still work if
the field is updated again.