BACKPORT: [media] v4l2-mem2mem: add v4l2_m2m_create_bufs helper

BUG=chrome-os-partner:33364
TEST=With all the patches in the series run the decoder JPEG test
	./test-jpeg -m 1 -f [input jpeg file] -o [output file]
		-v [decoder node]  -r [format] -s 1
	where:
		format should be a value from 0 to 9

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Kamil Debski <k.debski@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
(cherry picked from commit 8b94ca61d7065fa7fa7bdb08ce31a9385be5205b)
Signed-off-by: Abhilash Kesavan <a.kesavan@samsung.com>

Change-Id: I667621315bca7d5c802e86d081252e028b04c7df
Reviewed-on: https://chromium-review.googlesource.com/226152
Reviewed-by: Wei-Ning Huang <wnhuang@chromium.org>
Tested-by: Wei-Ning Huang <wnhuang@chromium.org>
Commit-Queue: Wei-Ning Huang <wnhuang@chromium.org>
Merge branch 'chromeos-3.8' of https://chromium.googlesource.com/chromiumos/third_party/kernel into chromeos-3.8