arm64: dts: qcom: ipq6018: Fix qmp usb3 phy node

Fix the following 'make dtbs_check' warning(s) by
using phy@ instead of lanes@ and by moving '#clock-cells' to
sub-node:

arch/arm64/boot/dts/qcom/ipq6018-cp01-c1.dt.yaml: ssphy@78000:
 'lane@78200' does not match any of the regexes: '^phy@[0-9a-f]+$', 'pinctrl-[0-9]+'

Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Rob Herring <robh@kernel.org>
Signed-off-by: Bhupesh Sharma <bhupesh.sharma@linaro.org>
Reviewed-by: Shawn Guo <shawn.guo@linaro.org>
[bjorn: s/clock-names/clock-cells/ per Shawn's feedback]
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20220228123019.382037-7-bhupesh.sharma@linaro.org