nubus: fix mis-indented statement

It seems this is the right way around because otherwise the len usage in
the outer loop would be pretty pointless.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>