input: touchscreen: add missing documentation for pinctrl

Add missing documentation for pincrl in Atmel and Synaptics
touch controller driver. Add support for pinctrl framework
for GPIO configuration so that the touch controller driver
is compatible with targets that use and targets that don't
use pinctrl framework. Also configure the gpio and pinctrl
in driver suspend/resume method for the run time power
consumption.

Change-Id: I2e8ee89a4c3e2ec4a63279852f4a30cdbf5bb0dc
Signed-off-by: Sarada Prasanna Garnayak <c_sgarna@codeaurora.org>