gpio: Move GE GPIO driver to reside within GPIO subsystem

The GE GPIO driver provides basic support (set direction, read/write state)
for the GPIO provided on some GE single board computers. This patch moves
the driver from the 86xx specific platform directrory to the GPIO subsystem
so that it can be used on non-86xx boards.

Signed-off-by: Martyn Welch <martyn.welch@ge.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>