staging: wfx: fix support for cipher AES_CMAC (multicast PMF)

staging: wfx: fix support for cipher AES_CMAC (multicast PMF)

When MFP is enabled, the multicast management frames are not protected,
in fact. Instead, but they should include an IE containing the MMIC of
the frames (i.e. a cryptographic signature).

Until now, the driver didn't correctly detect this kind of frames (they
are not marked protected but they are associated to a key) and didn't
ask to the device to encrypt them.

In add, the device is not able to generate the IE itself. Mac80211 has
to generate the IE and let the device compute the MMIC.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200825085828.399505-5-Jerome.Pouiller@silabs.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>