skylake: Finalize SMM in coreboot

Once we lock down the SPI BAR we need to tell SMM to re-init its
SPI driver or it will be unable to write ELOG events via SMI.

This SMI is also sent at the end of depthcharge so there was just
a window where SMI events could get lost.

BUG=chrome-os-partner:50076
BRANCH=glados
TEST=enable DEBUG_SMI, boot to dev screen, press power button and
see elog events get added without without transaction errors.

Change-Id: I1f14717b5e7f29c158dde8fd308bdbfb67eba41a
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: 60ca24c760c70e2ebe5f3e68f95d3ffdba0fef9e
Original-Change-Id: I4e323249f00954e290a6a30f515e34632681bfdd
Original-Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/326861
Original-Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/13697
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>

src/soc/intel/skylake/finalize.c

@@ -210,6 +210,9 @@ static void soc_finalize(void *unused)
 
 	soc_lockdown();
 
+	printk(BIOS_DEBUG, "Finalizing SMM.\n");
+	outb(APM_CNT_FINALIZE, APM_CNT);
+
 	/* Indicate finalize step with post code */
 	post_code(POST_OS_BOOT);
 }