mac80211: allow setting spatial reuse parameters from bss_conf

Store the OBSS PD parameters inside bss_conf when bringing up an AP and/or
when a station connects to an AP. This allows the driver to configure the
HW accordingly.

Signed-off-by: John Crispin <john@phrozen.org>
Link: https://lore.kernel.org/r/20190730163701.18836-3-john@phrozen.org
Signed-off-by: Johannes Berg <johannes.berg@intel.com>