drm/amdgpu: fix the warning bad bit shift operation for aca_error_type type

Filter invalid aca error types before performing a shift operation.

Signed-off-by: Jesse Zhang <Jesse.Zhang@amd.com>
Reviewed-by: Yang Wang <kevinyang.wang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>