drm/amdgpu/swsmu/aldebaran: fix check in is_dpm_running

If smu_cmn_get_enabled_mask() fails, return false to be
consistent with other asics.

Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: Lee Jones <lee.jones@linaro.org>
Reviewed-by: Lee Jones <lee.jones@linaro.org>