ARM: dts: qcom: msm8974: Drop redundant phy-names from DSI controller

phy-names has been marked deprecated. Remove it from the msm8974 DSI
controller block.

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20220907000105.786265-4-bryan.odonoghue@linaro.org