phy/rockchip: Add support for Innosilicon MIPI/LVDS/TTL PHY

The Innosilicon Video Combo PHY not only supports MIPI DSI,
but also LVDS and TTL functions with small die size and low
pin count. Customers can choose according to their own applications.

Signed-off-by: Wyon Bi <bivvy.bi@rock-chips.com>
[removed TTL mode for now, as it required a hook back into the dsi host]
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>