drm/amd/pm: add support to umd P-state function for vangogh

drm/amd/pm: add support to umd P-state function for vangogh

This patch is to add support to umd P-state function for vangogh.
It enables the "set" function of 3 sysfs nodes: pp_dpm_mclk,
pp_dpm_fclk, pp_dpm_socclk, the functions is used to set the DPM
frequency level of memclk/fclk/socclk.
Due to only after enabling the "power_dpm_force_performance_level"
sysfs node, it is allowed to set these three nodes,
so this patch also enables the "powe_dpm_force_performance_level"
sysfs node, which is used to change power profile.

Signed-off-by: Xiaojian Du <Xiaojian.Du@amd.com>
Reviewed-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>