drm/panel: Add Ilitek ILI9881c panel driver

The LHR050H41 panel is the panel shipped with the BananaPi M2-Magic, and is
based on the Ilitek ILI9881c Controller. Add a driver for it, modelled
after the other Ilitek controller drivers.

Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/acb5453112ab7c7b801cf4f1669e351b391e77e8.1527587352.git-series.maxime.ripard@bootlin.com