rtw88: remove misleading module parameter rtw_fw_support_lps

The module parameter rtw_fw_support_lps is misleading. It
is not used to represent the firmware's property, but to
determine if driver wants to ask firmware to enter LPS.

However, driver should better enable/disable PS through
cfg80211_ops::set_power_mgmt instead.
For example, one could use iw command to set PS state.

  $ sudo iw wlanX set power_save [on/off]

So rtw_fw_support_lps should be removed because it is
misleading and useless. Instead of checking the parameter,
set PS mode according to IEEE80211_CONF_PS.

Signed-off-by: Yan-Hsuan Chuang <yhchuang@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>