[media] m5mols: Don't ignore v4l2_ctrl_handler_setup() return value

v4l2_ctrl_handler_setup() may fail so check its return value when
restoring controls after device is powered on. While at it simplify
the m5mols_restore_function() a bit.

Acked-by: HeungJun Kim <riverful.kim@samsung.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>