dt-bindings: clock: mediatek,apmixedsys: Fix "mediatek,mt6779-apmixed" compatible

"mediatek,mt6779-apmixed" is the compatible string in use already, not
"mediatek,mt6779-apmixedsys".

Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://lore.kernel.org/r/20240807-dt-mediatek-clk-v1-1-e8d568abfd48@kernel.org


Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>