media: videobuf2-dma-contig: Invalidate vmap range before DMA range

Christoph suggests [1] that invalidating vmap range before
direct mapping range makes more sense.

[1]: https://lore.kernel.org/all/20220111085958.GA22795@lst.de/



Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>