clk: mediatek: mt8365-mm: fix DPI0 parent

To have a working display through DPI, a workaround has been
implemented downstream to add "mm_dpi0_dpi0" and "dpi0_sel" to
the DPI node. Shortly, that add an extra clock.

It seems consistent to have the "dpi0_sel" as parent.
Additionnaly, "vpll_dpix" isn't used/managed.

Then, set the "mm_dpi0_dpi0" parent clock to "dpi0_sel".

The new clock tree is:

clk26m
  lvdspll
    lvdspll_X (2, 4, 8, 16)
      dpi0_sel
        mm_dpi0_dpi0

Fixes: d46adccb

 ("clk: mediatek: add driver for MT8365 SoC")
Signed-off-by: Alexandre Mergnat <amergnat@baylibre.com>
Link: https://lore.kernel.org/r/20231023-display-support-v3-12-53388f3ed34b@baylibre.com
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>