wifi: rtw89: correct PS calculation for SUPPORTS_DYNAMIC_PS

wifi: rtw89: correct PS calculation for SUPPORTS_DYNAMIC_PS

This driver relies on IEEE80211_CONF_PS of hw->conf.flags to turn off PS or
turn on dynamic PS controlled by driver and firmware. Though this would be
incorrect, it did work before because the flag is always recalculated until
the commit 28977e790b5d ("wifi: mac80211: skip powersave recalc if driver SUPPORTS_DYNAMIC_PS")
is introduced by kernel 5.20 to skip to recalculate IEEE80211_CONF_PS
of hw->conf.flags if driver sets SUPPORTS_DYNAMIC_PS.

Correct this by doing recalculation while BSS_CHANGED_PS is changed and
interface is added or removed. For now, it is allowed to enter PS only if
single one station vif is working, and it could possible to have PS per
vif after firmware can support it. Without this fix, driver doesn't
enter PS anymore that causes higher power consumption.

Fixes: e3ec7017f6a2 ("rtw89: add Realtek 802.11ax driver")
Cc: stable@vger.kernel.org # 6.1+
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230527082939.11206-3-pkshih@realtek.com