cpufreq: acpi: Remove acpi_cpufreq_cpu_ready()

The ready() callback was implemented earlier for acpi-cpufreq driver as
we wanted to use policy->cpuinfo.max_freq for which the policy was
required to be verified.

That is no longer the case and we can do the pr_warn() right from
->init() callback now. Remove acpi_cpufreq_cpu_ready().

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