n 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.

It was slightly inconsistently though, since planes with only linear
modifier support haven't listed that explicitly. Fix that, and cc:
stable to allow userspace to rely on this. Again don't backport
further than where Paul's patch got added.

Cc: stable@vger.kernel.org # v5.1 +
Cc: Pekka Paalanen <pekka.paalanen@collabora.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Jonathan Hunter <jonathanh@nvidia.com>
Cc: linux-tegra@vger.kernel.org
Link: https://patchwork.freedesktop.org/patch/msgid/20210413094904.3736372-10-daniel.vetter@ffwll.ch
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