tools/memory-model: Code reorganization in lock.cat

tools/memory-model: Code reorganization in lock.cat

Code reorganization for the lock.cat file in tools/memory-model:

Improve the efficiency by ruling out right at the start RU events
(spin_is_locked() calls that return False) inside a critical section
for the same lock.

Improve the organization of the code for handling LF and RU events by
pulling the definitions of the pair-to-relation macro out from two
different complicated compound expressions, using a single standalone
definition instead.

Rewrite the calculations of the rf relation for LF and RU events, for
greater clarity.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Tested-by: Andrea Parri <parri.andrea@gmail.com>
Acked-by: Andrea Parri <parri.andrea@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>