staging: comedi: comedi_fops: make internal function static

The function do_become_nonbusy() is only referenced in this file.
Make it static.
Signed-off-by: NH Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/comedi_fops.c

@@ -2023,7 +2023,8 @@ static ssize_t comedi_read(struct file *file, char __user *buf, size_t nbytes,
 /*
    This function restores a subdevice to an idle state.
  */
-void do_become_nonbusy(struct comedi_device *dev, struct comedi_subdevice *s)
+static void do_become_nonbusy(struct comedi_device *dev,
+			      struct comedi_subdevice *s)
 {
 	struct comedi_async *async = s->async;