msm: camera: sensor: Add state validation for flash

Validate current flash state before turning on the flash.
Multiple calls to same state is a valid request in case of
dual camera. So the request is ignored is already present
in desired state.

Crs-Fixed: 1051259
Change-Id: Ifa2c4721a156c34c6d917ff950d648bea6cee50e
Signed-off-by: Rajesh Bondugula <rajeshb@codeaurora.org>