drm/amd/powerplay: Fix a bug for enabling ACDC gpio interrupt

Only enable it if it's supported rather than unconitionally.

Signed-off-by: Eric Yang <eric.yang2@amd.com>
Reviewed-by: Rex Zhu <Rex.Zhu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>