memtest86+: change the default baud rate to 115200

Most boards that coreboot supports support 115200 and use it by default.
Therefore, use it as default, as it’s hard to configure

Change-Id: I36d6d276cd87d646902a49b0287e1fb1830a98ab
Signed-off-by: Ben Gardner <gardner.ben@gmail.com>
Reviewed-on: https://review.coreboot.org/13930
Reviewed-by: Martin Roth <martinroth@google.com>
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
diff --git a/config.h b/config.h
index 7ef9994..102250d 100644
--- a/config.h
+++ b/config.h
@@ -48,7 +48,7 @@
 
 /* SERIAL_BAUD_RATE - Baud rate for the serial console */
 #ifndef SERIAL_BAUD_RATE
-#define SERIAL_BAUD_RATE 9600
+#define SERIAL_BAUD_RATE 115200
 #endif
 
 /* SCRN_DEBUG - extra check for SCREEN_BUFFER