drm/arm/malidp: Always list modifiers

drm/arm/malidp: Always list modifiers

Even when all we support is linear, make that explicit. Otherwise the
uapi is rather confusing.

Acked-by: Liviu Dudau <liviu.dudau@arm.com>
Acked-by: Pekka Paalanen <pekka.paalanen@collabora.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Cc: stable@vger.kernel.org
Cc: Pekka Paalanen <pekka.paalanen@collabora.com>
Cc: Liviu Dudau <liviu.dudau@arm.com>
Cc: Brian Starkey <brian.starkey@arm.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210427092018.832258-2-daniel.vetter@ffwll.ch