win7: Generalize volume-id for professional

Generalize volume-id to include 'N SP1' variant.
win7: Put pro n sp1 regex under correct architecture

In commit 39f22d2 (win7: Generalize volume-id for professional), I
generalized the regex of windows 7 professional to include N SP1 but I
ended up adding the regex for both i386 and x86_64 architectures under
i386.

This patch fixes that.