[media] ov2640: select sensor register bank before applying h/v-flip settings

We currently don't select the register bank in ov2640_s_ctrl, so we can end up
writing to DSP register 0x04 instead of sensor register 0x04.
This happens for example when calling ov2640_s_ctrl after ov2640_s_fmt.

Signed-off-by: Frank Schäfer <fschaefer.oss@googlemail.com>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>