xpt related hang on sparc64

[Mark Linimon]

On Fri, Jan 13, 2017 at 11:23:13PM -0700, Alan Somers wrote:
> That error message can mean many different things.  You need to boot
> in verbose mode to get a better idea.

As a test I created a netbootable image from -current the other day.
All I had available to test was an X1 which booted fine.  (It was
just lying around anyway.)

I can try one of the v210s or v215s if you continue to have trouble.

mcl