SERIAL: MIPS Swarm sb1250-duart.c driver needs module.h

This driver is a module and needs module.h, otherwise it will break when
we remove a bogus usage of module.h from one of the other MIPS headers.
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/3447/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

drivers/tty/serial/sb1250-duart.c

@@ -31,6 +31,7 @@
 #include <linux/interrupt.h>
 #include <linux/ioport.h>
 #include <linux/kernel.h>
+#include <linux/module.h>
 #include <linux/major.h>
 #include <linux/serial.h>
 #include <linux/serial_core.h>