msm: cam: isp: Fix camera freeze due to irq scheduling delay

Change the ISP context state machine to handle the IRQ scheduling delay.
Also change the spin_lock to spin_lock_bh to handle the race condition
between the tasklet and user thread.

Change-Id: I5273a3663bc67a629feb6a5b23dd3bb5e252c361
Signed-off-by: Jing Zhou <jzhou70@codeaurora.org>