locking/memory-barriers: Replace smp_cond_acquire() with smp_cond_load_acquire()

Amend the changes in commit:

  1f03e8d2 ("locking/barriers: Replace smp_cond_acquire() with smp_cond_load_acquire()")

... by updating the documentation accordingly.

Also remove some obsolete information related to the implementation.
Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Akira Yokosawa <akiyks@gmail.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Daniel Lustig <dlustig@nvidia.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Jade Alglave <j.alglave@ucl.ac.uk>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luc Maranget <luc.maranget@inria.fr>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: linux-arch@vger.kernel.org
Cc: parri.andrea@gmail.com
Link: http://lkml.kernel.org/r/20180926182920.27644-5-paulmck@linux.ibm.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

Documentation/memory-barriers.txt

@@ -471,8 +471,7 @@ And a couple of implicit varieties:
      operations after the ACQUIRE operation will appear to happen after the
      ACQUIRE operation with respect to the other components of the system.
      ACQUIRE operations include LOCK operations and both smp_load_acquire()
-     and smp_cond_acquire() operations. The later builds the necessary ACQUIRE
-     semantics from relying on a control dependency and smp_rmb().
+     and smp_cond_load_acquire() operations.
 
      Memory operations that occur before an ACQUIRE operation may appear to
      happen after it completes.