Make early x86 POST codes written to IO port optional

This continues the work done in patch 6b908d08ab
http://review.coreboot.org/#/c/1685/
and makes the early x86 post codes follow the same options.

Change-Id: Idf0c17b27b3516e79a9a53048bc203245f7c18ff
Signed-off-by: Martin Roth <martin.roth@se-eng.com>
Reviewed-on: http://review.coreboot.org/3237
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

src/include/cpu/x86/post_code.h

@@ -1,7 +1,12 @@
 
 #include <console/post_codes.h>
 
+
+#if CONFIG_IO_POST
 #define post_code(value)        \
 	movb    $value, %al;    \
-	outb    %al, $0x80
+	outb    %al, $CONFIG_IO_POST_PORT
 
+#else
+#define post_code(value)
+#endif