nl80211: fix netns separation

There are currently a few ways to "escape"
the network namespace and access a wiphy
that belongs to another namespace. Add a
netns argument to the relevant functions
to fix this.

One remaining issue with testmode will be
fixed in a follow-up patch.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --cc net/wireless/nl80211.c
Simple merge