ring-bufer: kernel-doc warning fixes

Also fixes a couple of typos

Link: http://lkml.kernel.org/r/1401992525-10417-1-git-send-email-fabf@skynet.be



Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Fabian Frederick <fabf@skynet.be>
[ Found this deep in the abyss of my INBOX ]
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>