cpufreq: Convert to using %pOF instead of full_name

Now that we have a custom printf format specifier, convert users of
full_name to use %pOF instead. This is preparation to remove storing
of the full path string for each node.

Signed-off-by: Rob Herring <robh@kernel.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Patrice Chotard <patrice.chotard@st.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>