powerpc: gpio driver for mpc8349/8572/8610 and compatible

Structured similar to the existing QE GPIO support.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
Acked-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>