staging: lustre: changed __u32 to __be32

Temporary variable is used only as __be32, for both assignments and reads,
but the type is inconsistent (__u32).

Signed-off-by: Nikola Jelic <nikola.jelic83@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>