drm/bridge: dw-hdmi: Add SCDC and TMDS Scrambling support

Add support for SCDC Setup for TMDS Clock > 3.4GHz and enable TMDS
Scrambling when supported or mandatory.

This patch also adds an helper to setup the control bit to support
the high TMDS Bit Period/TMDS Clock-Period Ratio as required with
TMDS Clock > 3.4GHz for HDMI2.0 3840x2160@60/50 modes.

These changes were based on work done by Huicong Xu <xhc@rock-chips.com>
and Nickey Yang <nickey.yang@rock-chips.com> to support HDMI2.0 modes
on the Rockchip 4.4 BSP kernel at [1]

[1] https://github.com/rockchip-linux/kernel/tree/release-4.4



Cc: Nickey Yang <nickey.yang@rock-chips.com>
Cc: Huicong Xu <xhc@rock-chips.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1549022873-40549-2-git-send-email-narmstrong@baylibre.com