ehci: remove duplicate debug_async_open() prototype in ehci-dbg.c

This patch removes the duplicate of debug_async_open() prototype following
three lines below the debug_async_open() declaration.
Signed-off-by: Xenia Ragiadakou <burzalodowa@gmail.com>
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/ehci-dbg.c

@@ -336,7 +336,6 @@ static inline void remove_debug_files (struct ehci_hcd *bus) { }
 static int debug_async_open(struct inode *, struct file *);
 static int debug_periodic_open(struct inode *, struct file *);
 static int debug_registers_open(struct inode *, struct file *);
-static int debug_async_open(struct inode *, struct file *);
 
 static ssize_t debug_output(struct file*, char __user*, size_t, loff_t*);
 static int debug_close(struct inode *, struct file *);