arm64: dts: qcom: msm8996: Stop using legacy clock names

MDSS and its friends complain about the DTS is using legacy clock names,
update these to silence the warnings.

Reviewed-by: Niklas Cassel <niklas.cassel@linaro.org>
Reviewed-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>