camera: fix `-Wunused-variable` compiler warnings

Test: add `USE_CAMERA_V4L2_HAL := true` to
      hardware/libhardware/modules/camera/3_4/Android.mk and build
      mmm hardware/libhardware/modules/camera/3_4
Change-Id: I2755278b739db0bb746a78d0b66e1f644a44ff19
Signed-off-by: Sergii Piatakov <sergii.piatakov@globallogic.com>
1 file changed