cpufreq / intel_pstate: Add kernel command line option disable intel_pstate.
When intel_pstate is configured into the kernel it will become the
preferred scaling driver for processors that it supports. Allow the
user to override this by adding:
intel_pstate=disable
on the kernel command line.
Signed-off-by: Dirk Brandewie <dirk.j.brandewie@intel.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>