drm/doc: Add amdgpu hwmon/power documentation (v2)

Document the hwmon and power control interfaces exposed
by the amdgpu driver.

v2: use section rather than chapter for now

Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
2 files changed