Blackfin: support console-over-JTAG

The Blackfin JTAG has the ability to pass data via a back-channel without
halting the processor.  Utilize that channel to emulate a console.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/common/devices.c b/common/devices.c
index ce3b7a0..38f1bbc 100644
--- a/common/devices.c
+++ b/common/devices.c
@@ -240,6 +240,9 @@
 #ifdef CONFIG_NETCONSOLE
 	drv_nc_init ();
 #endif
+#ifdef CONFIG_JTAG_CONSOLE
+	drv_jtag_console_init ();
+#endif
 
 	return (0);
 }