staging: lustre: ptlrpc: re-export lustre_swab_lov_mds_md

Being over zealous in removing unused EXPORT_SYMBOLs the function
lustre_swab_lov_mds_md exports were removed. They need to be
exported so this patch restores those EXPORT_SYMBOLS. Same
mistake was done when porting to the upstream client.

Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-on: http://review.whamcloud.com/14545
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-6486


Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: John L. Hammond <john.hammond@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>