dt-bindings: soc: mediatek: Add support for MT8188 VPPSYS

Add compatible for MT8188 VPP mutex, having different bits to activate
mute for various hardware IPs.

Acked-by: Conor Dooley <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: AngeloGioacchino Del Regno <[e-mail]>

Documentation/devicetree/bindings/soc/mediatek/mediatek,mutex.yaml

···
       - mediatek,mt8186-disp-mutex
       - mediatek,mt8186-mdp3-mutex
       - mediatek,mt8188-disp-mutex
+      - mediatek,mt8188-vpp-mutex
       - mediatek,mt8192-disp-mutex
       - mediatek,mt8195-disp-mutex
       - mediatek,mt8195-vpp-mutex