Determine whether VCN using unified queue in sw_init, instead of calling
functions later on.

v2: fix coding style
Signed-off-by: Boyuan Zhang <boyuan.zhang@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Ruijing Dong <ruijing.dong@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>