DRM/Radeon: Fix Load Detection on legacy primary DAC.

commit 83325d072185899b706de2956170b246585aaec9 upstream.

An uninitialized variable led to broken load detection.

Signed-off-by: Egbert Eich <eich@suse.de>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>