CHROMIUM: [media] rk3288-vpu: Implement basic V4L2 APIs for decoder

CHROMIUM: [media] rk3288-vpu: Implement basic V4L2 APIs for decoder

This patch adds implementation of basic V4L2 APIs for decoder part of
the driver. It is still missing the hardware specific part, including
the hardware specific controls containing certain data precalculated
in userspace.

BUG=chrome-os-partner:33728
TEST=compile

Signed-off-by: Tomasz Figa <tfiga@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/237617
Reviewed-by: Pawel Osciak <posciak@chromium.org>
Change-Id: I3cad74aad3c6c4ac5e6b2123b5d93e3173b74c7a
Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
Signed-off-by: Yakir Yang <ykk@rock-chips.com>