msm: camera: isp: Avoid locking in IRQ context

Check if the thread is IRQ handler to avoid deadlock
trying to lock. The interrupt handler currently holds
the lock, so any other API being called from IRQ context
should not try to lock, else there will be recursion
leading to deadlock.

Change-Id: I6f70234b430286c94a0b558ebeb5b4393c06d995
Signed-off-by: Harsh Shah <harshs@codeaurora.org>