cpufreq: amd-pstate: Add a kernel config option to set default mode

Users are having more success with amd-pstate since the introduction
of EPP and Guided modes.  To expose the driver to more users by default
introduce a kernel configuration option for setting the default mode.

Users can use an integer to map out which default mode they want to use
in lieu of a kernel command line option.

This will default to EPP, but only if:
 1) The CPU supports an MSR.
 2) The system profile is identified
 3) The system profile is identified as a non-server by the FADT.

Link: https://gitlab.freedesktop.org/hadess/power-profiles-daemon/-/merge_requests/121


Acked-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Co-developed-by: Perry Yuan <perry.yuan@amd.com>
Signed-off-by: Perry Yuan <perry.yuan@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>