ARM: dts: msm: add release pinctrl state for touchscreen GPIOs

Touchscreen controllers are field-swappable on both customer
devices and internal reference platforms. Current touch driver
architecture for Focaltech does not release the mux owner of
GPIO pins used by it whenever there is a failure in its probe
routine. As a result of this, other touchscreen driver are not
able to take ownership of these GPIO pins in their probe routines,
causing them to fail. This patch provides a solution for this
scenario by adding a new pinctrl state to DT node of Focaltech
touch controller. This state is parsed by Focaltech driver and
is selected during its remove/error cleanup path, which thereby
releases the mux owner of these GPIO pins. The patch also adds
the corresponding pingroup for touchscreen GPIOs in pinctrl's
DT include files. This node doesn't have a pin-function
property associated with it and is explicitly used by each
touch driver to release the mux ownership of its GPIO pins
during error paths in driver. Presently, the change is
applicable to msm8916 and msm8939 only.

Change-Id: Ied1f4c7b7d950b9902d64ba4cb677d226a2a963e
Signed-off-by: Himanshu Aggarwal <haggarwa@codeaurora.org>