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)

Makefile.inc

@@ -62,6 +62,11 @@ endif
 smm-c-ccopts:=-D__SMM__
 smm-S-ccopts:=-D__SMM__
 
+# SMM TSEG base is dynamic
+ifeq ($(CONFIG_SMM_TSEG),y)
+smm-c-ccopts += -fpic
+endif
+
 ramstage-c-deps:=$$(OPTION_TABLE_H)
 romstage-c-deps:=$$(OPTION_TABLE_H)