imx-drm: fix plane atomic_update regression

- request modeset if plane offsets changed, only the plane base
  address can be changed without disabling the plane IDMAC channel,
  stop returning an error if a valid YUV plane configuration with
  different U/V offsets from the currently active plane is requested.
- merge ipu_plane_atomic_set_base into atomic_update, also fixes a
  regression introduced by commit 81d553545a15 ("drm/imx: ipuv3-plane: Skip
  setting u/vbo only when we don't need modeset") where U/V offsets were not
  set corretly when enabling YUV planes without a modeset.
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