This patch fix incorrect handling of LSI v3 MegaRAID metadata.

Problem reports:
http://www.freebsd.org/cgi/query-pr.cgi?pr=92786
http://www.freebsd.org/cgi/query-pr.cgi?pr=95260
http://www.freebsd.org/cgi/query-pr.cgi?pr=101819

Thanks to Andrey Groshev and Dmitry Kutsanov for testing.

(c) Andrey V. Elsukov <bu7cher [at] yandex.ru>