drm/panel: Add Samsung S6D7AA0 panel controller driver

drm/panel: Add Samsung S6D7AA0 panel controller driver

Initial driver for S6D7AA0-controlled panels. Currently, the following
panels are supported:

 - S6D7AA0-LSL080AL02 (Samsung Galaxy Tab 3 8.0)
 - S6D7AA0-LSL080AL03 (Samsung Galaxy Tab A 8.0 2015)
 - S6D7AA0-LTL101AT01 (Samsung Galaxy Tab A 9.7 2015)

It should be possible to extend this driver to work with other panels
using this IC.

Tested-by: Nikita Travkin <[email protected]> #ltl101at01
Signed-off-by: Artur Weber <[email protected]>
Reviewed-by: Neil Armstrong <[email protected]>
Signed-off-by: Neil Armstrong <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]