The UART support is needed in SMM in order for DEBUG_SMI to function. BUG=chrome-os-partner:54262 TEST=Ran on reef with DEBUG_SMI enabled. Can observed SMI messages. Change-Id: Ibd6b12e27d5776046b400adf72f24133b9e54af8 Signed-off-by: Aaron Durbin <adurbin@chromium.org> Reviewed-on: https://review.coreboot.org/15151 Tested-by: build bot (Jenkins) Reviewed-by: Furquan Shaikh <furquan@google.com>