HGST SAS link loss (was: mpt(4) timeout recovery improvements)

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

> I still don't know what the root cause for the ,,Phy x: Link Status 
> Unknown'' events is
Just for the record: The root cause is probably a ``self initiated reset''
of the Hitachi (HGST) disk due to a bug in the A100 firmware (HGST calls
that ``microcode'').
Fortunately, the update process is documented. So if someone needs a HGST 
disk firmware update utility for NetBSD, I can help.