docs: Fix typos and drop/fix dead links in RCU documentation

docs: Fix typos and drop/fix dead links in RCU documentation

It appears the Compaq link moved to a machine at HP for a while
after the merger of the two, but that doesn't work either.  A search
of HP for "wiz_2637" (w and w/o html suffix) comes up empty.

Since the references aren't critical to the documents we remove them.

Also, the lkml.kernel.org/g links have been broken for ages, so replace
them with lore.kernel.org/r links - standardize on lore for all links too.

Note that we put off fixing these 4y ago - presumably thinking that a
treewide fixup was pending.  Probably safe to go fix the RCU ones now.

https://lore.kernel.org/r/20160915144926.GD10850@linux.vnet.ibm.com/

Cc: Michael Opdenacker <michael.opdenacker@free-electrons.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>