drm/amd/pm: fix SMU13 runpm hang due to unintentional workaround

The workaround designed for some specific ASICs is wrongly applied
to SMU13 ASICs. That leads to some runpm hang.

Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Reviewed-by: Feifei Xu <Feifei.Xu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org