media: smiapp: unlock on error in smiapp_start_streaming()

We added two new error paths to smiapp_start_streaming(), but we can't
return directly without dropping the "sensor->mutex" lock.

Fixes: f8c4352c

 ("media: smiapp: Move binning configuration to streaming start")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>