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

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

  2e4f5382d12a4 ("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>

Documentation/memory-barriers.txt

@@ -31,15 +31,15 @@ Contents:
 
  (*) Implicit kernel memory barriers.
 
-     - Locking functions.
+     - Lock acquisition functions.
      - Interrupt disabling functions.
      - Sleep and wake-up functions.
      - Miscellaneous functions.
 
- (*) Inter-CPU locking barrier effects.
+ (*) Inter-CPU acquiring barrier effects.
 
-     - Locks vs memory accesses.
-     - Locks vs I/O accesses.
+     - Acquires vs memory accesses.
+     - Acquires vs I/O accesses.
 
  (*) Where are memory barriers needed?
 
@@ -1859,7 +1859,7 @@ This is a variation on the mandatory write barrier that causes writes to weakly
 ordered I/O regions to be partially ordered.  Its effects may go beyond the
 CPU->Hardware interface and actually affect the hardware at some level.
 
-See the subsection "Locks vs I/O accesses" for more information.
+See the subsection "Acquires vs I/O accesses" for more information.
 
 
 ===============================
@@ -1874,8 +1874,8 @@ provide more substantial guarantees, but these may not be relied upon outside
 of arch specific code.
 
 
-ACQUIRING FUNCTIONS
--------------------
+LOCK ACQUISITION FUNCTIONS
+--------------------------
 
 The Linux kernel has a number of locking constructs: