gpio: ge: convert to use basic mmio gpio library

This patch converts GE GPIO driver to use basic_mmio_gpio
generic library.

Signed-off-by: Kamlakant Patel <kamlakant.patel@linaro.org>
Acked-by: Martyn Welch <martyn.welch@ge.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>