[media] videobuf2-core: call __setup_offsets only for mmap memory type

__setup_offsets fills the v4l2_planes' mem_offset fields, which is only valid
for V4L2_MEMORY_MMAP type buffers. For V4L2_MEMORY_DMABUF and _USERPTR buffers,
this incorrectly overwrites the fd and userptr fields.

Reported-by: Michael Olbrich <[e-mail]>
Signed-off-by: Philipp Zabel <[e-mail]>
Acked-by: Marek Szyprowski <[e-mail]>
Acked-by: Pawel Osciak <[e-mail]>
Acked-by: Hans Verkuil <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/v4l2-core/videobuf2-core.c

···
 		q->bufs[q->num_buffers + buffer] = vb;
 	}
 
-	__setup_offsets(q, buffer);
+	if (memory == V4L2_MEMORY_MMAP)
+		__setup_offsets(q, buffer);
 
 	dprintk(1, "Allocated %d buffers, %d plane(s) each\n",
 			buffer, num_planes);