miimon & mode must be set before other parameters, and then not changed
again. Prior commit f671e0a28 per bug #421757 introduced a small logic
error. Fixed & refactored to prevent it happening as easily.
X-Gentoo-Bug: 447790
X-Gentoo-Bug-URL: https://bugs.gentoo.org/show_bug.cgi?id=447790
Signed-off-by: Robin H. Johnson <robbat2@gentoo.org>