[ofw] ib-diags: compatability issue with ibstat

[Hefty, Sean]

commit 1344cb3feacafc462440dabfa5997c5205486d83 added support for FDR10 in a way that is not compatible with Windows support.  Windows does not use files to read attribute information.

I will probably need to obtain the necessary information using ibverbs on windows by reading port attributes.  I don't think FDR10 support is available through ibverbs on linux yet, but would this be acceptable?  Is there some other way that you'd like to handle this?  The other option I can think of is moving is_fdr10() and sys_read_string() out of ibstat.c and into a linux specific file, so that windows can provide its own implementation.  Thoughts?

- Sean