drm/radeon: bind fan control on SI cards to hwmon interface

This adds a possibility to control fan on SI parts
via exported hwmon variables. Note that automatic
ucode fan management pauses if you choose to enable
manual fan control.  Use with caution!

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --cc drivers/gpu/drm/radeon/radeon_asic.c
Simple merge

diff --cc drivers/gpu/drm/radeon/radeon_asic.h
Simple merge

diff --cc drivers/gpu/drm/radeon/si_dpm.c
Simple merge

diff --cc drivers/gpu/drm/radeon/si_dpm.h
Simple merge