sun4i-csi: call _vb2_fop_release instead of v4l2_fh_release

This driver didn't call _vb2_fop_release in the sun4i_csi_release
function. Without that call the vb2 queue is not properly canceled and
buffers may not be freed.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>