Use INTEL_GEN to simplify the code for SKL+ platforms.

v2:
- split the enabling code into final one to identify any regression.

Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Reviewed-by: NZhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: NFei Jiang <fei.jiang@intel.com>
Signed-off-by: Nfred gao <fred.gao@intel.com>
Signed-off-by: NZhenyu Wang <zhenyuw@linux.intel.com>