SMM: Avoid use of global variables in SMI handler

Using global variables with the TSEG is a bad idea because
they are not relocated properly right now.  Instead make
the variables static and add accessor functions for the
rest of SMM to use.

At the same time drop the tcg/smi1 pointers as they are
not setup or ever used.  (the debug output is added back
in a subsequent commit)

Change-Id: If0b2d47df4e482ead71bf713c1ef748da840073b
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: http://review.coreboot.org/1764
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

src/include/cpu/x86/smm.h

@@ -384,4 +384,7 @@ u32 smi_get_tseg_base(void);
 void tseg_relocate(void **ptr);
 #endif
 
+/* Get PMBASE address */
+u16 smm_get_pmbase(void);
+
 #endif