Restore identification of VDEVs using non-native block size.

    NAME         STATE     READ WRITE CKSUM
    dsk02        ONLINE       0     0     0
      mirror-0   ONLINE       0     0     0
        ada1s4a  ONLINE       0     0     0
        ada2s4a  ONLINE       0     0     0  block size: 512B configured,
					     4096B native

Reviewed by: tsoome (previous FreeBSD phab version)
Differential Revision: https://reviews.freebsd.org/D26880

Upstream commit: 3928ec53395fcc26be7844dd6b63df757166c281
Reviewed-by: Matt Macy <mmacy@FreeBSD.org>
Reviewed-by: Toomas Soome <tsoome@me.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed off by: Cy Schubert <cy@FreeBSD.org>
Closes #11088