x86: Work around compiler code generation bug with -Os

Some versions of gcc generate incorrect code for the inet_check_attr()
function, apparently due to a totally bogus index -> pointer comparison
transformation.

At least "gcc version 4.0.1 20050727 (Red Hat 4.0.1-5)" from FC4 is
affected, possibly others too.

This changes the function subtly so that the buggy gcc transformation
doesn't trigger.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>