LU-7623 lnet: remove useless cast

LU-7623 lnet: remove useless cast

In the cleanup of the user land / kernel pointers a
small cleanup was missed which removed a cast no
longer needed for a call of lnet_ping(). This brings
us into sync with the upstream client.

Change-Id: Ib281aaac7f2a1516d8586fbf3d10dee18cd77873
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-on: http://review.whamcloud.com/18950
Tested-by: Jenkins
Reviewed-by: Frank Zago <fzago@cray.com>
Reviewed-by: Christopher J. Morrone <morrone2@llnl.gov>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>