locking/Documentation: Fix missed s/lock/acquire renames

The terms 'lock'/'unlock' were changed to 'acquire'/'release' by the
following commit:

  2e4f5382 ("locking/doc: Rename LOCK/UNLOCK to ACQUIRE/RELEASE")

However, the commit missed to change the table of contents - fix that.

Also, the dumb rename changed the section name 'Locking functions' to an
actively misleading 'Acquiring functions' section name.

Rename it to 'Lock acquisition functions' instead.

Suggested-by: David Howells <dhowells@redhat.com>
Signed-off-by: SeongJae Park <sj38.park@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: bobby.prani@gmail.com
Cc: dipankar@in.ibm.com
Cc: dvhart@linux.intel.com
Cc: edumazet@google.com
Cc: fweisbec@gmail.com
Cc: jiangshanlai@gmail.com
Cc: josh@joshtriplett.org
Cc: mathieu.desnoyers@efficios.com
Cc: oleg@redhat.com
Cc: rostedt@goodmis.org
Link: http://lkml.kernel.org/r/1460476375-27803-2-git-send-email-paulmck@linux.vnet.ibm.com


[ Rewrote the changelog. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>