msm: camera: fd: Need to use irqsave for spin_lock

fd_core->spin_lock is used in irq() function, so any other place
using it should call spin_lock_irqsave and spin_unlock_irqrestore.
Without this change, we can have deadlock on this spin_lock.

Change-Id: I2b2f0699a8c8af9c67e3028df10d45b533000259
Signed-off-by: Harsh Shah <harshs@codeaurora.org>