drm/amdgpu: fix a reversed condition

This test was reversed so it would end up leading to vddnb value
can't be read via hwmon on APU.

Reviewed-by: Evan Quan <[email protected]>
Reviewed-by: Alex Deucher <[email protected]>
Signed-off-by: Rex Zhu <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>
Cc: [email protected]
1 file changed