usb: imx21-hcd: Include missing linux/module.h

Include <linux/module.h>, so that the following errors are fixed:

drivers/usb/host/imx21-hcd.c:1929:20: error: expected declaration specifiers or '...' before string constant
drivers/usb/host/imx21-hcd.c:1930:15: error: expected declaration specifiers or '...' before string constant
drivers/usb/host/imx21-hcd.c:1931:16: error: expected declaration specifiers or '...' before string constant
drivers/usb/host/imx21-hcd.c:1932:14: error: expected declaration specifiers or '...' before string constant
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/imx21-hcd.c

@@ -58,6 +58,7 @@
 #include <linux/usb.h>
 #include <linux/usb/hcd.h>
 #include <linux/dma-mapping.h>
+#include <linux/module.h>
 
 #include "imx21-hcd.h"