dt-bindings: phy: brcm,brcmstb-usb-phy: Fix error in "compatible" conditional schema

The conditional if/then schema has an error as the "enum" values have
"const" in them. Drop the "const".
Signed-off-by: Rob Herring <robh@kernel.org>
Fixes: 46b616c1 ("dt-bindings: phy: brcm, brcmstb-usb-phy: add BCM4908 binding")
Acked-by: Rafał Miłecki <rafal@milecki.pl>
Message-ID: <20230621230958.3815818-1-robh@kernel.org>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Documentation/devicetree/bindings/phy/brcm,brcmstb-usb-phy.yaml

@@ -115,8 +115,8 @@ allOf:
         compatible:
           contains:
             enum:
-              - const: brcm,bcm4908-usb-phy
-              - const: brcm,brcmstb-usb-phy
+              - brcm,bcm4908-usb-phy
+              - brcm,brcmstb-usb-phy
     then:
       properties:
         reg: