USB: musb: Prevent multiple includes of musb.h

Add #ifndef to musb header file to prevent multiple inclusions.

Signed-off-by: Mark A. Greer <[e-mail]>
Signed-off-by: David Brownell <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

include/linux/usb/musb.h

···
  * key configuration differences between boards.
  */
 
+#ifndef __LINUX_USB_MUSB_H
+#define __LINUX_USB_MUSB_H
+
 /* The USB role is defined by the connector used on the board, so long as
  * standards are being followed.  (Developer boards sometimes won't.)
  */
···
 extern int tusb6010_platform_retime(unsigned is_refclk);
 
 #endif	/* OMAP2 */
+
+#endif /* __LINUX_USB_MUSB_H */