clk: qcom: gpucc-sm6350: Introduce index-based clk lookup

clk: qcom: gpucc-sm6350: Introduce index-based clk lookup

Add the nowadays-prefered and marginally faster way of looking up parent
clocks in the device tree. It also allows for clock-names-independent
operation, so long as the order (which is enforced by schema) is kept.

Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Link: https://lore.kernel.org/r/20230315-topic-lagoon_gpu-v2-1-afcdfb18bb13@linaro.org
Signed-off-by: Bjorn Andersson <andersson@kernel.org>