drm/panel: Add driver for Samsung S6D16D0 panel

The Samsung S6D16D0 is a simple comman mode only DSI display
that is used on the ST-Ericsson Ux500 reference design
TVK1281618 user interface board (UIB).

Cc: Andrzej Hajda <a.hajda@samsung.com>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20181023074630.29186-2-linus.walleij@linaro.org