MFC r358555, r358799-r358800

r358555:
cpufreq_dt: Improve multiple opp support

When looking for cpu with the same OPP starts from the root /cpus node
so each instance of cpufreq_dt will now each cpu with the same operating
point.
Also test that the node we are testing have the property "device_type" set
to be equal to "cpu".
While here add more debug printfs (off by defaults).

r358799:
cpufreq_dt: Fix r358555

Before skipping the current cpu when trying to find the ones that
have the same opp, record that this one have this opp.

Reported by: mmel
X-MFC-With: r358555

r358800:
cpufreq: Unbreak build.