drivers: pinctrl: pinctrl-msm: clear pending irq before enabling

Clear the pending irq at GIC before enabling.

This will help in clearing any erroneous interrupts that would
have gotten latched when the GPIO interrupt is not in use.

Change-Id: Id1d6b8d5305bdc06d8f55b510a7d0d2d296a28e3
Signed-off-by: Maulik Shah <mkshah@codeaurora.org>