[media] soc-camera: mt9m111: Fix auto-exposure control

Commit f9bd5843 changed V4L2_CID_EXPOSURE_AUTO
from boolean to enum, and commit af8425c5
changed the creation of this control into a menu for the mt9m111. However,
mt9m111_set_autoexposure() is still interpreting the value set for this control
as a boolean, which also conflicts with the default value of this control set to
V4L2_EXPOSURE_AUTO (0).
This patch makes mt9m111_set_autoexposure() interpret the value set for
V4L2_CID_EXPOSURE_AUTO as defined by enum v4l2_exposure_auto_type.

Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>
Tested-by: Javier Martin <javier.martin@vista-silicon.com>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>