[media] media: vb2: fix userptr VMA release seq

Align vb2 user pointer VMA release sequence with munmap.
Do vm_ops->vm_close before release file.

Signed-off-by: Yu Tang <ytang5@marvell.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>