drm/rockchip: Add support for afbc

This patch adds support for afbc handling. afbc is a compressed format
which reduces the necessary memory bandwidth.

Co-developed-by: Mark Yao <mark.yao@rock-chips.com>
Signed-off-by: Mark Yao <mark.yao@rock-chips.com>
Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
Reviewed-by: Sandy Huang <hjc@rock-chips.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200311145541.29186-7-andrzej.p@collabora.com