cpufreq: Remove ->resolve_freq()

Commit e3c06236 ("cpufreq: add cpufreq_driver_resolve_freq()")
introduced this callback, back in 2016, for drivers that provide the
->target() callback.

The kernel hasn't seen a single user of it in the past 5 years and
it is not likely to be used any time soon.

Remove it for now.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
[ rjw: Changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>