msm: camera: sensor: Change initializer to 0 instead of -EINVAL

When FLASH_LOW / FLASH_HIGH is called multiple times the function
must return success without error if the flash is already in
desired state. But due to initializer -EINVAL is returned.
So setting initializer to 0.

CRs-Fixed: 1062351
Signed-off-by: Rajesh Bondugula <rajeshb@codeaurora.org>
Change-Id: Ie6ff66e272005bc83b3bb6ea8c353d4eb9088048