drm/radeon/dpm/atom: fix broken gcc harder

See bugs:
https://bugs.freedesktop.org/show_bug.cgi?id=66932
https://bugs.freedesktop.org/show_bug.cgi?id=66972
https://bugs.freedesktop.org/show_bug.cgi?id=66945



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