Add support for the LCD panels that must be driven with the
Sharp-specific signals SPL, CLS, REV, PS.

An example of such panel is the LS020B1DD01D supported by the
panel-simple DRM panel driver.
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20190627182114.27299-2-paul@crapouillou.net
# *** extracted tags ***
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>