drm/panel: simple: Support TI nspire panels

This adds support for the TI nspire panels to the simple panel
roster. This code is based on arch/arm/mach-nspire/clcd.c.
This includes likely the first grayscale panel supported.

These panels will be used with the PL11x DRM driver.

Cc: Daniel Tang <dt.tangr@gmail.com>
Cc: Fabian Vogt <fabian@ritter-vogt.de>
Tested-by: Fabian Vogt <fabian@ritter-vogt.de>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190805085847.25554-4-linus.walleij@linaro.org