dt-bindings: ufs: drop unused/old ufs-qcom PHY bindings

The Qualcomm UFS PHY bindings are documented in
bindings/phy/qcom,qmp-phy.yaml and the compatibles from separate file
bindings/ufs/ufs-qcom.txt are not used at all.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220306111125.116455-5-krzysztof.kozlowski@canonical.com