drm/panel: s6d27a1: Add driver for Samsung S6D27A1 display panel

This adds a driver for Samsung S6D27A1 display controller and panel.
This panel is found in the Samsung GT-I8160 mobile phone,
and possibly some other mobile phones.

This display needs manufacturer commands to configure it;
the commands used in this driver were taken from downstream driver
by Gareth Phillips; sadly, there is almost no documentation on what they
actually do.

This driver re-uses the DBI infrastructure to communicate with the display.

This driver is heavily based on WideChips WS2401 display controller
driver by Linus Walleij and on other panel drivers for reference.

Signed-off-by: Markuss Broks <markuss.broks@gmail.com>
[Up reset out time to 120 ms]
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210807133111.5935-3-markuss.broks@gmail.com