[ofw] WinOF IPoIB fails with a subnet prefix other than the default

[Sean Hefty]

>If I change the subnet prefix to something like 2001000000000000 then I never
>get IPoIB connectivity.  Whatever is happening, sometimes the system becomes
>highly unresponsive, and  it also leans hard on the Linux system running the
>subnet manager, making it very sluggish.  My intention is to use a router, but
>problem happens even with no router on the subnet.

Unlike the Linux stack, I'm not aware of any work done on the WinOF stack to
support IB routers.  I'm not sure how much effort would be involved for this.