staging: wfx: fix BA when MFP is disabled but BSS is MFP capable

staging: wfx: fix BA when MFP is disabled but BSS is MFP capable

The protection of the management frames is mainly done by mac80211.
However, frames for the management of the BlockAck sessions are directly
sent by the device. These frames have to be protected if MFP is in use.
So the driver has to pass the MFP configuration to the device.

Until now, the driver directly read the RSN IE of the BSS. However, it
didn't work when the BSS was MFP capable (ieee80211w=1) and the local
device has disabled MFP (ieee80211w=0).

This patch read the MFP information directly from the struct
ieee80211_sta. This information take into account the MFP negotiated
during the association. In addition, the code is far simpler.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200825085828.399505-3-Jerome.Pouiller@silabs.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>