docs/memory-barriers.txt: Fixup long lines

docs/memory-barriers.txt: Fixup long lines

Substitution of "data dependency barrier" with "address-dependency
barrier" left quite a lot of lines exceeding 80 columns.

Reflow those lines as well as a few short ones not related to
the substitution.

No changes in documentation text.

Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Will Deacon <will@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Andrea Parri <parri.andrea@gmail.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Daniel Lustig <dlustig@nvidia.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>