ARM: S5PC100: gpio.h cleanup

This patch renames gpio related registers from s5pc1xx to s5pc100 to
better match the plat-s5p framework style. GPIO_MP* defines now used
anywhere thus has been removed.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>