The 'dev' argument is only optional for ethX devices, for others it is
mandatory, so we should always include it.
Also tweak when promisc mode is applied to bridges.
Patches submitted by Denis Kaganovich <mahatma@bspu.unibel.by>.
X-Gentoo-Bug: #431204
X-Gentoo-Bug-URL: https://bugs.gentoo.org/show_bug.cgi?id=431204
Signed-off-by: Robin H. Johnson <robbat2@gentoo.org>