soc/intel/cannonlake: Add support for EMMC DLL update

Add option to have customized DLL setting for EMMC interface to make
EMMC able to run at HS400 speed.

BUG=None

Change-Id: I38bc022d8c05dd1fbd03dc26aa6f33cd249e8248
Signed-off-by: Lijian Zhao <lijian.zhao@intel.com>
Reviewed-on: https://review.coreboot.org/23600
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
2 files changed