mac80211: Allocate a sync skcipher explicitly for FILS AEAD

The skcipher could have been of the async variant which may return from
skcipher_encrypt() with -EINPROGRESS after having queued the request.
The FILS AEAD implementation here does not have code for dealing with
that possibility, so allocate a sync cipher explicitly to avoid
potential issues with hardware accelerators.

This is based on the patch sent out by Ard.

Fixes: 39404fee ("mac80211: FILS AEAD protection for station mode association frames")
Reported-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>