USB: gadget rndis: send notifications

It turns out that atomic_inc_return() returns the *new* value
not the original one, so the logic in rndis_response_available()
kept the first RNDIS response notification from getting out.
This prevented interoperation with MS-Windows (but not Linux).

Fix this to make RNDIS behave again.

Signed-off-by: Richard Röjfors <[e-mail]>
Signed-off-by: David Brownell <[e-mail]>
Cc: stable <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/gadget/f_rndis.c

···
 	__le32				*data = req->buf;
 	int				status;
 
-	if (atomic_inc_return(&rndis->notify_count))
+	if (atomic_inc_return(&rndis->notify_count) != 1)
 		return;
 
 	/* Send RNDIS RESPONSE_AVAILABLE notification; a