drm/tiny: add support for tft displays based on ilitek,ili9486

This adds support fot ilitek,ili9486 based displays with shift register
in front of controller.
Ozzmaker,Piscreen and Waveshare,rpi-lcd-35 are such displays.

Acked-by: Sam Ravnborg <sam@ravnborg.org> (v4)
Reviewed-by: Noralf Tronnes <noralf@tronnes.org> (v4)
Signed-off-by: Kamlesh Gurudasani <kamlesh.gurudasani@gmail.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
[fixed checkpatch warnings]
Link: https://patchwork.freedesktop.org/patch/msgid/a9c8065c3ef7707650630b3b21a0c01d725fc5a0.1581270802.git.kamlesh.gurudasani@gmail.com