sh: use gpiolib

This patch updates the SuperH gpio code to make use of gpiolib. The
gpiolib callbacks get() and set() are lockless, but we use our own
spinlock for the other operations to make sure hardware register
bitfield accesses stay atomic.

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>