LU-334 llite: Add LPROC_LL_OSC_{READ,WRITE}.

LU-334 llite: Add LPROC_LL_OSC_{READ,WRITE}.

This patch adds quick and easy access to aggregate OSC BRW (bytes on
the wire) statistics through llite.  To accomplish this, we pass the
number of bytes transferred by a successful request to
cl_req_completion(), and on to ll_stats_ops_tally() by way of the
ccc_req_completion().

Signed-off-by: John L. Hammond <jhammond@tacc.utexas.edu>
Change-Id: I4b464c27f6dc87fcc19d35b2bc45dc7cb9bf7741
Reviewed-on: http://review.whamcloud.com/1341
Reviewed-by: Richard Henwood <rhenwood@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Jinshan Xiong <jay@whamcloud.com>
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>