staging: most: cdev: fix chrdev_region leak in mod_exit

It looks like v4.18-rc1 commit [0] which upstreams mld-1.8.0
commit [1] missed to fix the memory leak in mod_exit function.

Do it now.

[0] aba258b7 ("staging: most: cdev: fix chrdev_region leak")
[1] https://github.com/microchip-ais/linux/commit/a2d8f7ae7ea381
    ("staging: most: cdev: fix leak for chrdev_region")
Signed-off-by: Suresh Udipi <sudipi@jp.adit-jv.com>
Signed-off-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Acked-by: Christian Gromm <christian.gromm@microchip.com>
Fixes: aba258b7 ("staging: most: cdev: fix chrdev_region leak")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/most/cdev/cdev.c

@@ -555,7 +555,7 @@ static void __exit mod_exit(void)
 		destroy_cdev(c);
 		destroy_channel(c);
 	}
-	unregister_chrdev_region(comp.devno, 1);
+	unregister_chrdev_region(comp.devno, CHRDEV_REGION_SIZE);
 	ida_destroy(&comp.minor_id);
 	class_destroy(comp.class);
 }