msm: camera: Added flash_led_release function

For LED flash, led_release function was missing.
Due to that, msm close was getting stuck and device can't restart.
Added null check for function pointers.

Change-Id: I1c28a92add51f5544f0b16d25c74a544c8380b19
Signed-off-by: Suman <Mukherjee&lt;sumam@codeaurora.org>