staging/lustre: clean up and remove libcfs/linux/linux-fs.c

filp_user_write() is open coded in libcfs_kkuc_msg_put(). All
other functions/macros have no user at all. So we can remove
the file.

Signed-off-by: Peng Tao <tao.peng@emc.com>
Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>