mfi(4) users and foreign configs

If you have a mfi(4) device – in other words, a LSI MegaRAID SAS driver – you can now see/import/clear/etc. foreign configurations, thanks to this commit from Sascha Wildner, tested by Francois Tigeot, and originally from FreeBSD.

For the confused, ‘foreign’ means any disk hooked to a RAID controller that isn’t part of a configuration the RAID device already knows about.  A replacement disk, or more worryingly, a good disk gone bad/unrecognizable.  (I’ve had both.)