staging: comedi: make some variables unsigned in comedi_write()

In `comedi_write()`, the `n` and `m` variables are of type `int`.
Change them to `unsigned int` as they are used to measure a positive
number of bytes.  The `count` variable is also of type `int` and holds
the returned number of bytes written.  Change it to type `ssize_t` to
match the function's return type.
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/comedi_fops.c

@@ -2303,7 +2303,9 @@ static ssize_t comedi_write(struct file *file, const char __user *buf,
 {
 	struct comedi_subdevice *s;
 	struct comedi_async *async;
-	int n, m, count = 0, retval = 0;
+	unsigned int n, m;
+	ssize_t count = 0;
+	int retval = 0;
 	DECLARE_WAITQUEUE(wait, current);
 	struct comedi_file *cfp = file->private_data;
 	struct comedi_device *dev = cfp->dev;