cpufreq: Disallow ->resolve_freq() for drivers providing ->target_index()

The handlers provided by cpufreq core are sufficient for resolving the
frequency for drivers providing ->target_index(), as the core already
has the frequency table and so ->resolve_freq() isn't required for such
platforms.

This patch disallows drivers with ->target_index() callback to use the
->resolve_freq() callback.

Also, it fixes a potential kernel crash for drivers providing ->target()
but no ->resolve_freq().

Fixes: e3c06236 "cpufreq: add cpufreq_driver_resolve_freq()"
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>