cpufreq: handle cpufreq being disabled for all exported function.

When disable_cpufreq() is called some exported functions are still
being used that do not have a check for cpufreq being disabled.

Add a disabled check into cpufreq_cpu_get() to return NULL if
cpufreq is disabled this covers most of the exported functions. For
the exported functions that do not call cpufreq_cpu_get() add an
explicit check.

Signed-off-by: Dirk Brandewie <dirk.j.brandewie@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
cpufreq: Add a get_current_driver helper

Add a helper function to return cpufreq_driver->name.

Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Conflicts:
	include/linux/cpufreq.h
Revert " cpufreq: Don't use cpu removed during cpufreq_driver_unregister"

This reverts commit 07320f38099f09421ee43cc686db81c74a746598.
Changed GPU onload freq from 307,384,512Mhz to 384,460,537Mhz respectivly