ring-buffer-benchmark: Fix the wrong type

The macro 'module_param' shows that the type of the
variable disable_reader and write_iteration is unsigned
integer. so, we change their type form int to unsigned int.

Link: http://lkml.kernel.org/r/1433923927-67782-1-git-send-email-long.wanglong@huawei.com



Signed-off-by: Wang Long <long.wanglong@huawei.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>