Remove leftover smi_get_tseg_base

Change-Id: I8e694f37c8709efd702208aa005096ebf1f3abb5
Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
Reviewed-on: http://review.coreboot.org/10356
Tested-by: build bot (Jenkins)
Reviewed-by: Edward O'Callaghan <edward.ocallaghan@koparo.com>

src/include/cpu/x86/smm.h

@@ -487,8 +487,6 @@ void mainboard_smi_sleep(u8 slp_typ);
 
 #if !CONFIG_SMM_TSEG
 void smi_release_lock(void);
-#else
-#define smi_get_tseg_base() 0
 #endif
 
 /* Get PMBASE address */