LU-7623 lmv: Properly mark lmv_fid2path uarg argment as __user

LU-7623 lmv: Properly mark lmv_fid2path uarg argment as __user

This makes sparse happy too.

Change-Id: Ice8067168af9a6d13900e6224d3224dbb6bf0541
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Reviewed-on: http://review.whamcloud.com/17782
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Frank Zago <fzago@cray.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>