media: ov7740: fix unbalanced pm_runtime_get/put

Avoid returning without decrement the usage count in s_ctrl().

Cc: Wenyou Yang <wenyou.yang@microchip.com>
Cc: Eugen Hristev <eugen.hristev@microchip.com>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>