commit cb3e4e7c upstream.

Need to properly unregister the hwmon device on driver
unload.

v2: minor clean up

bug:
https://bugzilla.kernel.org/show_bug.cgi?id=73931Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>