staging: lustre: lnet: return of an error code should be negative

Return value of error codes should typically be negative.
Issue reported by checkpatch.pl

Signed-off-by: Sumit Pundir <pundirsumit11@gmail.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>