arm64: dts: msm8953: Drop unsupported dwc3 flag

Property phy_mode according to binding checker does not exist,
drop it.
Signed-off-by: Adam Skladowski <a39.skl@gmail.com>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230325112852.18841-3-a39.skl@gmail.com

arch/arm64/boot/dts/qcom/msm8953.dtsi

@@ -977,7 +977,6 @@ usb3_dwc3: usb@7000000 {
 				snps,hird-threshold = /bits/ 8 <0x00>;
 
 				maximum-speed = "high-speed";
-				phy_mode = "utmi";
 			};
 		};