Add the missing "qref" clock used by the SM8450 UFS QMP PHY to the
binding.

Note that the "qref" clock was added to sm8450.dtsi by commit
07fa917a ("arm64: dts: qcom: sm8450: add ufs nodes") but the binding
was never updated to match.

Fixes: e04121ba ("dt-bindings: phy: qcom,qmp: Add SM8450 UFS phy compatible")
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Link: https://lore.kernel.org/r/20220830112923.3725-17-johan+linaro@kernel.orgSigned-off-by: Vinod Koul <vkoul@kernel.org>