dt-bindings: mediatek: add compatible for MT6873/8192 pwrap

This adds dt-binding documentation of pwrap for Mediatek MT6873/8192
SoCs Platform.
Signed-off-by: Hsin-Hsiung Wang <hsin-hsiung.wang@mediatek.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/1615563286-22126-4-git-send-email-hsin-hsiung.wang@mediatek.comSigned-off-by: Matthias Brugger <matthias.bgg@gmail.com>

Documentation/devicetree/bindings/soc/mediatek/pwrap.txt

@@ -22,6 +22,7 @@ Required properties in pwrap device node.
 	"mediatek,mt6765-pwrap" for MT6765 SoCs
 	"mediatek,mt6779-pwrap" for MT6779 SoCs
 	"mediatek,mt6797-pwrap" for MT6797 SoCs
+	"mediatek,mt6873-pwrap" for MT6873/8192 SoCs
 	"mediatek,mt7622-pwrap" for MT7622 SoCs
 	"mediatek,mt8135-pwrap" for MT8135 SoCs
 	"mediatek,mt8173-pwrap" for MT8173 SoCs