CHROMIUM: [media] rk3288-vpu: Require kernel mapping only for encoder output

CHROMIUM: [media] rk3288-vpu: Require kernel mapping only for encoder output

For rk3288-vpu, kernel mapping of video buffers is required only for
encoder bitstream output buffers for additional bistream formatting. Any
other buffers can be allocated without kernel mapping, greatly
conserving the limited pool of vmalloc memory.

This patch modifies the rk3288-vpu driver to use the newly added vb2-dc
interface to create two separate allocation contexts, one for
allocations with kernel mapping and one without.

BUG=chrome-os-partner:38873
TEST=vda/vea unit tests

Signed-off-by: Tomasz Figa <tfiga@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/265364
Reviewed-by: Pawel Osciak <posciak@chromium.org>
Change-Id: I4154802dda2329934dea675a242d67e80b925db0
Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
Signed-off-by: Yakir Yang <ykk@rock-chips.com>