msm: camera: sensor: Check name for existence of flash

Check length of flash name for its existance.
eventually is_flash_suported flag can be removed
as it would be redundant.

Change-Id: Ibb0dd7e35dce80aff3c45dc7a5720d368094cc3c
Signed-off-by: Rajesh Bondugula <rajeshb@codeaurora.org>