Here's the first patch that introduces the context:

+choice
+	prompt "Method for KGDB communication"
+	depends on KGDB
+	default KGDB_ONLY_MODULES
+	help
+	  There are a number of different ways in which you can communicate
+	  with KGDB.  The most common is via serial, with the 8250 driver
+	  (should your hardware have an 8250, or ns1655x style uart).
+	  Another option is to use the NETPOLL framework and UDP, should
+	  your ethernet card support this.  Other options may exist.
+	  You can elect to have one core I/O driver that is built into the
+	  kernel for debugging as the kernel is booting, or using only
+	  kernel modules.
+


Here's the hunk that modifies it:

@@ -193,7 +193,7 @@ config KGDB_CONSOLE
 choice
 	prompt "Method for KGDB communication"
 	depends on KGDB
-	default KGDB_ONLY_MODULES
+	default KGDB_8250_NOMODULE
 	default KGDB_MPSC if SERIAL_MPSC
 	help
 	  There are a number of different ways in which you can communicate

Note the second 'default' line.