media: ov5640: fix auto gain & exposure when changing mode

Ensure that auto gain and auto exposure are well restored
when changing mode.

Signed-off-by: Hugues Fruchet <hugues.fruchet@st.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Tested-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>