Blackfin: uart: add multiple serial support

This brings CONFIG_SERIAL_MULTI support to the Blackfin on-chip UARTs.
Ends up adding only ~512bytes per additional UART.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/common/serial.c b/common/serial.c
index 8ebf9a5..7a69fc1 100644
--- a/common/serial.c
+++ b/common/serial.c
@@ -173,6 +173,9 @@
 	serial_register(&serial6_device);
 #endif
 #endif
+#if defined(CONFIG_SYS_BFIN_UART)
+	serial_register_bfin_uart();
+#endif
 	serial_assign (default_serial_console ()->name);
 }