The compatible string is changed to fsl,mpic on all e500 platforms, to
advertise the existence of BRR1.  This matches what the device tree will
have on real hardware.

With MPIC v4.2 max_cpu can be increased from 15 to 32.
Signed-off-by: NScott Wood <scottwood@freescale.com>
Signed-off-by: NAlexander Graf <agraf@suse.de>