drm/rockchip: add support for gamma table

drm/rockchip: add support for gamma table

Introduce support for rockchip gamma table,

Rockchip have two version gamma table design:
The old version design was introduced by Dominik Behr's gamma patch
(https://chromium-review.googlesource.com/272209):
 Gamma table has to be uploaded when the LUT is disabled which only takes
 effect at the end of a frame, therefore actual hardware updates is done
 from a worker and can take more than one frame.

In order to solve gamma table switch issues, after rk3399,
H/W add a gamma table update mechanism, can update without lut disable.

And gamma table's size also has two version:
  one is 10 bit per component, 1024 entries,
  the other one is 8 bit per component, 256 entries

Change-Id: I8145d1c42a28d57f11e95d24be2341011360334d
Signed-off-by: Dominik Behr <dbehr@chromium.org>
Signed-off-by: Mark Yao <mark.yao@rock-chips.com>