wifi: mac80211, cfg80211: Export michael_mic() and move it to cfg80211

wifi: mac80211, cfg80211: Export michael_mic() and move it to cfg80211

Export michael_mic() so that the ath11k and ath12k drivers can call it.
In addition, move it from mac80211 to cfg80211 so that the ipw2x00
drivers, which depend on cfg80211 but not mac80211, can also call it.

Currently these drivers have their own local implementations of
michael_mic() based on crypto_shash, which is redundant and inefficient.
By consolidating all the Michael MIC code into cfg80211, we'll be able
to remove the duplicate Michael MIC code in the crypto/ directory.

Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Link: https://patch.msgid.link/20260408030651.80336-3-ebiggers@kernel.org
Signed-off-by: Johannes Berg <johannes.berg@intel.com>