Remove allow_fb_modifiers setting in this driver. The allow_fb_modifiers
flag was removed.

Signed-off-by: Tomohito Esaki <etom@igel.co.jp>
Fixes: 3d082157 ("drm: remove allow_fb_modifiers")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220204023635.15496-1-etom@igel.co.jp