kvm/ppc/mpic: import hw/openpic.c from QEMU

This is QEMU's hw/openpic.c from commit
abd8d4a4d6dfea7ddea72f095f993e1de941614e ("Update version for
1.4.0-rc0"), run through Lindent with no other changes to ease merging
future changes between Linux and QEMU.  Remaining style issues
(including those introduced by Lindent) will be fixed in a later patch.
Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Alexander Graf <agraf@suse.de>