clk: mediatek: mt2701-mm: add missing dummy clk

clk: mediatek: mt2701-mm: add missing dummy clk

Add dummy clk which was missed during the conversion to
mtk_clk_pdev_probe() and is required for the existing DT bindings to
keep working.

Fixes: 65c10c50c9c7 ("clk: mediatek: Migrate to mtk_clk_pdev_probe() for multimedia clocks")
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Link: https://lore.kernel.org/r/9de23440fcba1ffef9e77d58c9f505105e57a250.1734300668.git.daniel@makrotopia.org
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>