usb: usbtest: Remove stack VLA usage

The kernel would like to have all stack VLA usage removed[1]. We
already have a pre-processor constant defined MAX_SGLEN. We can use
this instead of the variable param-sglen.

[1]: https://lkml.org/lkml/2018/3/7/621

Signed-off-by: Tobin C. Harding <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/misc/usbtest.c

···
 	unsigned		i;
 	unsigned long		packets = 0;
 	int			status = 0;
-	struct urb		*urbs[param->sglen];
+	struct urb		*urbs[MAX_SGLEN];
 
 	if (!param->sglen || param->iterations > UINT_MAX / param->sglen)
+		return -EINVAL;
+
+	if (param->sglen > MAX_SGLEN)
 		return -EINVAL;
 
 	memset(&context, 0, sizeof(context));