nl80211: don't hold RTNL in color change request

It's not necessary to hold the RTNL across color change
requests, since all the inner locking needs only the
wiphy mutex which we already hold as well.

Fixes: 0d2ab3ae ("nl80211: add support for BSS coloring")
Link: https://lore.kernel.org/r/20220414140402.32e03e8c261b.I5e7dc6bc563a129b938c43298da6bb4e812400a5@changeid


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