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