gpio: msm: Clear the interrupt status before unmasking

After the change to keep the RAW_STATUS_EN always on, the
interrupt status bit was latched and could be set during
other (non-interrupt) activity on the GPIO line. This would
end up triggering the interrupt as soon as it was unmasked.
Hence, clear the interrupt status before unmasking the gpio
interrupt. This keeps the behavior and expectations same as
when the RAW_STATUS_EN was toggled and it prevented the
interrupt status to be updated while the interrupt was masked.

Change-Id: I3ccb31b5d8a7efe93f8253d4aff4a1c44281163f
CRs-Fixed: 346861
Signed-off-by: Rohit Vaswani <rvaswani@codeaurora.org>