mpt.4: Warn about unexpected behaviour on older controllers

Older controllers have errata which causes the disk controller to wrap
data to other LBAs, causing data to be overwritten. [1]

While here, fix a small typo.

1: https://www.broadcom.com/support/knowledgebase/1211161496563/3-terabyte-3tb-capacity-drives-on-lsi-megaraid-and-3ware-control

PR: 220343
Submitted by: Sebastian Oswald <sebastian at rostwald.de>
Reviewed by: 0mp
Event: January 2021 Bugathon
Differential Revision: <https://reviews.freebsd.org/D28201