Documentation/robust-futex-API: Count properly to 4

Documentation/robust-futex-API: Count properly to 4

A strictly monotonically increasing sequence is normally used in
numbered lists as they provide an intuitive ordering of the
elements.

However, in situations where race conditions can appear, this
assumption breaks down and you can end up with unpredictable
results, leading to a rather confusing list :-)

This changes the numbered list 1,2,2,2 to the more intuitive
1,2,3,4.

Introduced in:

  2eec9ad91f71 [PATCH] lightweight robust futexes: docs

Signed-off-by: Henrik Austad <henrik@austad.us>
Link: http://lkml.kernel.org/r/1385590680-8110-1-git-send-email-henrik@austad.us
Signed-off-by: Ingo Molnar <mingo@kernel.org>