staging: lustre: osc: debug to match extent to brw RPC

staging: lustre: osc: debug to match extent to brw RPC

Currently, it's difficult to match brw RPCs to objects and
extents from client logs.  This patch adds a D_RPCTRACE
debug message giving the necessary information.

Signed-off-by: Patrick Farrell <paf@cray.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-5531
Reviewed-on: http://review.whamcloud.com/11548
Reviewed-by: Alexey Lyashkov <alexey.lyashkov@seagate.com>
Reviewed-by: Ann Koehler <amk@cray.com>
Reviewed-by: Ryan Haasken <haasken@cray.com>
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>