locktorture: Rename readers_bind/writers_bind to bind_readers/bind_writers

This commit renames the readers_bind and writers_bind module parameters
to bind_readers and bind_writers, respectively.  This provides added
clarity via the imperative mode and better organizes the documentation.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>