drm/panel: Add support for Raydium RM67191 panel driver

This patch adds Raydium RM67191 TFT LCD panel driver (MIPI-DSI
protocol).

Signed-off-by: Robert Chiras <robert.chiras@nxp.com>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/1561550907-9733-3-git-send-email-robert.chiras@nxp.com