Revert "drm/sun4i: drv: Allow framebuffer modifiers in mode config"

This reverts commit 9db9c0cf.

Setting mode_config.allow_fb_modifiers manually is completely
unnecessary. It is set automatically by drm_universal_plane_init() based
on the fact if modifier list is provided or not. Even more, it breaks
DE2 and DE3 as they don't support any modifiers beside linear. Modifiers
aware applications can be confused by provided empty modifier list - at
least linear modifier should be included, but it's not for DE2 and DE3.

Fixes: 9db9c0cf

 ("drm/sun4i: drv: Allow framebuffer modifiers in mode config")
Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Reviewed-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20200126065937.9564-1-jernej.skrabec@siol.net