[openib-general] add guid to struct ib_device

[Sean Hefty]

Is there any objection to adding the node_guid to struct ib_device?

The CM queries for this, and it looks like SRP does too.  To support per device 
listens from userspace, I was considering adding the same functionality to uCM 
as well.

I didn't see where RNICs have this concept; although, the spec does allow for 
vendor specific data.

- Sean