ppc: Add P7/P8 Power Management instructions

This adds the ISA 2.06 and later power management instructions
(doze, nap, sleep and rvwinkle) and associated wakeup cause testing
in LPCR

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
[clg: fixed checkpatch.pl errors ]
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>