NTB: Rename some variables/functions to match Linux

No functional change.

Still part of the huge e26a5843 rewrite. I'm trying to make it less of
a complete rewrite in the FreeBSD version of the driver. Still, it
helps if our names match Linux.

Obtained from: Linux (e26a5843) (Dual BSD/GPL driver)
Sponsored by: EMC / Isilon Storage Division