[media] v4l: ti-vpe: Use video_device_release_empty

The video_device struct is currently embedded in the driver data struct vpe_dev.
A vpe_dev instance is allocated by the driver, and the memory for the vfd is a
part of this struct.

The v4l2 core, however, manages the removal of the vfd region, through the
video_device's .release() op, which currently is the helper
video_device_release. This causes memory corruption, and leads to issues when
we try to re-insert the vpe module.

Use the video_device_release_empty helper function instead.

Reviewed-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Archit Taneja <archit@ti.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>