drm/amd/powerplay: export thermal range through temp sysfs

Populate the hwmon temp range as part of thermal controller setup.

Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>