Add support to run SMM handler in TSEG instead of ASEG

Traditionally coreboot's SMM handler runs in ASEG (0xa0000),
"behind" the graphics memory. This approach has two issues:
- It limits the possible size of the SMM handler (and the
  number of CPUs supported in a system)
- It's not considered a supported path anymore in newer CPUs.

Change-Id: I9f2877e46873ab2ea8f1157ead4bc644a50be19e
Signed-off-by: Duncan Laurie <dlaurie@google.com>
Acked-by: Stefan Reinauer <reinauer@google.com>
Reviewed-on: http://review.coreboot.org/842
Reviewed-by: Peter Stuge <peter@stuge.se>
Tested-by: build bot (Jenkins)

src/console/vtxprintf.c

@@ -6,6 +6,7 @@
 
 #include <string.h>
 #include <div64.h>
+#include <console/console.h>
 #include <console/vtxprintf.h>
 
 /* haha, don't need ctype.c */
@@ -115,6 +116,11 @@ int vtxprintf(void (*tx_byte)(unsigned char byte), const char *fmt, va_list args
 
 	int count;
 
+#if defined(__SMM__) && CONFIG_SMM_TSEG
+	/* Fix pointer in TSEG */
+	tx_byte = console_tx_byte;
+#endif
+
 	for (count=0; *fmt ; ++fmt) {
 		if (*fmt != '%') {
 			tx_byte(*fmt), count++;