USB: use function attribute __maybe_unused

Substitute USB instances of __attribute__ ((unused)) functions with the
newly introduced __maybe_unused.

Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/host/ohci-dbg.c b/drivers/usb/host/ohci-dbg.c
index 273d5dd..6f9e43e 100644
--- a/drivers/usb/host/ohci-dbg.c
+++ b/drivers/usb/host/ohci-dbg.c
@@ -23,7 +23,7 @@
 /* debug| print the main components of an URB
  * small: 0) header + data packets 1) just header
  */
-static void __attribute__((unused))
+static void __maybe_unused
 urb_print (struct urb * urb, char * str, int small)
 {
 	unsigned int pipe= urb->pipe;
@@ -338,7 +338,7 @@
 }
 
 /* caller MUST own hcd spinlock if verbose is set! */
-static void __attribute__((unused))
+static void __maybe_unused
 ohci_dump_ed (const struct ohci_hcd *ohci, const char *label,
 		const struct ed *ed, int verbose)
 {