drbd: fix max_segment_size initialization

blk_queue_make_request() internally calls blk_set_default_limits(),
so calling blk_queue_max_segment_size() before is useless.
Ergo: move the call to blk_queue_max_segment_size() down a few lines.

Impact:
If, after a fresh modprobe, you first connect a Diskless drbd,
then attach, this could result in a DRBD Protocol Error at first.
The next connection attempt would then succeeded.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>