msm: camera: sensor: Add flash support capability in sensor library.

Add flash support capability in sensor library to check for the
existence of flash. sub-dev id is determined by validating
flash existence from sensor library.

Change-Id: Iadb7ef7172d88cb970681b716fdd8de91976e1fd
Signed-off-by: Rajesh Bondugula <rajeshb@codeaurora.org>