On the first vdev open ignore impossible ashift hints

If on the first open device's logical ashift is bigger than set
by pool's ashift property, ignore the last as unusable instead of
creating vdev that will fail most of I/Os due to misalignment.

Reviewed-by: Rob Norris <robn@despairlabs.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Ameer Hamza <ahamza@ixsystems.com>
Signed-off-by: Alexander Motin <mav@FreeBSD.org>
Sponsored by: iXsystems, Inc.
Closes #16690