dt-bindings: phy: qcom,qmp: Add 'power-domains' property

Fix the following 'make dtbs_check' error with the 'qcom,qmp-phy'
bindings:
 arch/arm64/boot/dts/qcom/sm8150-mtp.dtb: phy@1d87000:
  'power-domains' 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>