[PATCH] knfsd: nfsd4: refactor exp_pseudoroot

We could be using more common code in exp_pseudoroot().  This will also
simplify some changes we need to make later.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>