drm/nouveau: Don't set allow_fb_modifiers explicitly

drm/nouveau: Don't set allow_fb_modifiers explicitly

Since

commit db245b0c549d4ec6964e3b714e81bec1c8f6ad80
Author: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Date:   Fri Jan 4 09:56:10 2019 +0100

    drm: Auto-set allow_fb_modifiers when given modifiers at plane init

this is done automatically as part of plane init, if drivers set the
modifier list correctly. Which is the case here.

Note that this fixes an inconsistency: We've set the cap everywhere,
but only nv50+ supports modifiers. Hence cc stable, but not further
back then the patch from Paul.

Reviewed-by: Lyude Paul <lyude@redhat.com>
Cc: stable@vger.kernel.org # v5.1 +
Cc: Pekka Paalanen <pekka.paalanen@collabora.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: nouveau@lists.freedesktop.org
Link: https://patchwork.freedesktop.org/patch/msgid/20210427092018.832258-6-daniel.vetter@ffwll.ch