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: NIlpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>