staging: lustre: lmv: access lum_stripe_offset as little endian

By the time that a struct lmv_user_md reaches lmv_placement_policy()
it has already been converted to little endian. Therefore use the
appropriate macros around accesses to this this field. This issue was
found by rewriting the definition of struct lmv_user_md to use the
__leXX typedefs and running sparse.

Signed-off-by: John L. Hammond <john.hammond@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-4738
Reviewed-on: http://review.whamcloud.com/9671


Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Swapnil Pimpale <spimpale@ddn.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>