cpufreq: scmi: Prepare to move OF parsing of domain-id to cpufreq

cpufreq: scmi: Prepare to move OF parsing of domain-id to cpufreq

The OF parsing of the clock domain specifier seems to better belong in the
scmi cpufreq driver, rather than being implemented behind the generic
->device_domain_id() perf protocol ops.

To prepare to remove the ->device_domain_id() ops, let's implement the OF
parsing in the scmi cpufreq driver instead.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Link: https://lore.kernel.org/r/20230825112633.236607-4-ulf.hansson@linaro.org
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>