soc/intel/common: Add common smihandler code

Provide default handler for some SMI events. Provide the framework for
extracting data from SMM Save State area for processors with SMM revision
30100 and 30101.
The SOC specific code should initialize southbridge_smi with event
handlers. For SMM Save state handling, SOC code should implement
get_smm_save_state_ops which initializes the SOC specific ops for SMM Save
State handling.

Change-Id: I0aefb6dbb2b1cac5961f9e43f4752b5929235df3
Signed-off-by: Hannah Williams <hannah.williams@intel.com>
Reviewed-on: https://review.coreboot.org/14615
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/include/elog.h

@@ -169,9 +169,7 @@ static inline int elog_smbios_write_type15(unsigned long *current,
 }
 #endif
 
-#if CONFIG_ELOG_GSMI
 extern u32 gsmi_exec(u8 command, u32 *param);
-#endif
 
 #if CONFIG_ELOG_BOOT_COUNT
 u32 boot_count_read(void);