Newly introduced mode_set callback in engine structure is a much better
place for setting mixer output size and interlace mode for the following
reasons:
1. Aforementioned properties change only when mode changes, so it's
   enough to be set only once per mode set. Currently it's done whenever
   properties of primary plane are changed.
2. It's assumed that primary plane will always cover whole screen. While
   this is true most of the time, it's not always. DE2/3 planes are
   universal and mostly equal in functionality. There is no reason to
   add artificial limitation to primary planes.
3. The current code only works for UI layers, but some mixers do not
   have any UI layers.
Signed-off-by: Jernej Skrabec <jernej.skrabec@gmail.com>
[Samuel: update commit message]
Signed-off-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20220424162633.12369-9-samuel@sholland.org