usb: gadget: lpc32xx_udc: fix build error with debugfs enabled

If CONFIG_USB_GADGET_DEBUG_FILES is enabled, lpc32xx_udc breaks
compilation because of a missing include file.
Signed-off-by: Alexandre Pereira da Silva <aletes.xgr@gmail.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/lpc32xx_udc.c

@@ -61,6 +61,7 @@
 #include <mach/irqs.h>
 #include <mach/board.h>
 #ifdef CONFIG_USB_GADGET_DEBUG_FILES
+#include <linux/debugfs.h>
 #include <linux/seq_file.h>
 #endif