mac80211_hwsim: enforce PS_MANUAL_POLL to be set after PS_ENABLED

Enforce using PS_MANUAL_POLL in ps hwsim debugfs to trigger a poll,
only if PS_ENABLED was set before.
This is required due to commit c9491367b759 ("mac80211: always update the
PM state of a peer on MGMT / DATA frames") that enforces the ap to
check only mgmt/data frames ps bit, and then update station's power save
accordingly.
When sending only ps-poll (control frame) the ap will not be aware that
the station entered power save.
Setting ps enable before triggering ps_poll, will send NDP with PM bit
enabled first.

Signed-off-by: Adiel Aloni <adiel.aloni@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>