backports: backport sysfs api in wireless

backports: backport sysfs api in wireless

Older kernel versions do not support the new sysfs api with dev_groups.
This makes net/wireless/sysfs.c use the old api on older kernels.

This is a backport of this commit:
commit f0bc99c84349ce87af5b35839d19bfb17bb9b27f
Author: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date:   Wed Jul 24 15:05:35 2013 -0700

    net: wireless: convert class code to use dev_groups

This was mostly done by Johannes Berg <johannes@sipsolutions.net>.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Cc: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Luis R. Rodriguez <mcgrof@do-not-panic.com>