media: bdisp: fix memleak on release

If a process is interrupted while accessing the video device and the
device lock is contended, release() could return early and fail to free
related resources.

Note that the return value of the v4l2 release file operation is
ignored.

Fixes: 28ffeebb ("[media] bdisp: 2D blitter driver using v4l2 mem2mem framework")
Cc: stable <stable@vger.kernel.org>     # 4.2
Signed-off-by: Johan Hovold <johan@kernel.org>
Reviewed-by: Fabien Dessenne <fabien.dessenne@st.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>