Input: egalax_ts - get gpio from devicetree

Input: egalax_ts - get gpio from devicetree

The irq_to_gpio() is old, most platforms use GENERIC_GPIO framework
and don't support this API anymore.

The i.MX6q sabrelite platform equips an egalax touchscreen controller,
and this platform already transfered to GENERIC_GPIO framework, to
support this driver, we use a more generic way to get gpio.

Add a return value checking for waking up the controller in the probe
function, this guarantee only a workable device can pass init.

[dmitry.torokhov@gmail.com: Make driver depend on CONFIG_OF as it is
 now required.]

Acked-by Zhang Jiejing <jiejing.zhang@freescale.com>
Reviewed-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Hui Wang <jason77.wang@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>