sb/intel/common: Add common code for SMM setup and smihandler

This moves the sandybridge both smm setup and smihandler code to a
common place.

Tested on Thinkpad X220, still boots, resume to and from S3 is fine
so smihandler is still working fine.

Change-Id: I28e2e6ad1e95a9e14462a456726a144ccdc63ec9
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/23427
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

src/southbridge/intel/common/Kconfig

@@ -22,6 +22,9 @@ config SOUTHBRIDGE_INTEL_COMMON_RCBA_PIRQ
 config HAVE_INTEL_CHIPSET_LOCKDOWN
 	def_bool n
 
+config SOUTHBRIDGE_INTEL_COMMON_SMM
+	def_bool n
+
 config INTEL_CHIPSET_LOCKDOWN
 	depends on HAVE_INTEL_CHIPSET_LOCKDOWN && HAVE_SMI_HANDLER && !CHROMEOS
 	#ChromeOS's payload seems to handle finalization on its on.