Update description for X-Gene standby GPIO controller DTS binding to
support GPIO line configuration as input, output or external IRQ pin.
Signed-off-by: NY Vo <yvo@apm.com>
Signed-off-by: NQuan Nguyen <qnguyen@apm.com>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>