This reverts commit 46431d9c.

This commit fixes a bug in upstream commit a136f59c ("vb2: Move
buffer cache synchronisation to prepare from queue") which isn't
present in 4.4.

So as a result you get an UNBALANCED message in the kernel log if
this patch is applied:

vb2:   counters for queue ffffffc0f3687478, buffer 3: UNBALANCED!
vb2:     buf_init: 1 buf_cleanup: 1 buf_prepare: 805 buf_finish: 805
vb2:     buf_queue: 806 buf_done: 806
vb2:     alloc: 0 put: 0 prepare: 806 finish: 805 mmap: 0
vb2:     get_userptr: 0 put_userptr: 0
vb2:     attach_dmabuf: 1 detach_dmabuf: 1 map_dmabuf: 805 unmap_dmabuf: 805
vb2:     get_dmabuf: 0 num_users: 1609 vaddr: 0 cookie: 805

Reverting this patch solves this regression.
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>