media: omap3isp: Add missed v4l2_ctrl_handler_free() for preview_init_entities()

preview_init_entities() does not call v4l2_ctrl_handler_free() when
it fails.
Add the missed function to fix it.

Fixes: de1135d4 ("[media] omap3isp: CCDC, preview engine and resizer")
Signed-off-by: Chuhong Yuan <hslester96@gmail.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>