input: atmel_mxt_ts: Secure touch fixes for multicore and i2c bus clock

When starting the secure touch during a swipe operation
the interrupt handler is often executed on a different core than
the one requesting the secure touch. This can cause an xPU
violation when the i2c bus is acquired by TrustZone.
We now make sure the interrupt handler is done, on any core, before
acknoledging the request to enable the secure touch mode.
Additional fix for a typo releasing the clock used by the i2c
bus when the session is over.

Change-Id: I87dba21c7011fc56cf7574afb372c621dc748f80
Acked-by: Christian Bolis <cbolis@qti.qualcomm.com>
Signed-off-by: Amy Maloche <amaloche@codeaurora.org>