Make POST codes written to IO port optional

This adds more configurability to POST codes. The current assumption
is that POST codes should be written to an IO port (e.g. LPC) if POST
codes are enabled. This changes the assumption so that POST codes can
be written to the serial console without being written to an IO port.

This enables POST codes by default using "default y" to avoid
changing current behavior.

Change-Id: I3db91c358ccb1557096983c4d07f70b2e872c4b3
Signed-off-by: David Hendricks <dhendrix@chromium.org>
Reviewed-on: http://review.coreboot.org/1685
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/console/post.c

@@ -100,7 +100,9 @@ void post_code(uint8_t value)
 #if CONFIG_CMOS_POST
 	cmos_post_code(value);
 #endif
-	outb(value, CONFIG_POST_PORT);
+#if CONFIG_IO_POST
+	outb(value, CONFIG_IO_POST_PORT);
+#endif
 #endif
 	mainboard_post(value);
 }