wifi: mac80211: remove DEAUTH_NEED_MGD_TX_PREP

wifi: mac80211: remove DEAUTH_NEED_MGD_TX_PREP

This flag is annoying because it puts a lot of logic into mac80211
that could just as well be in the driver (only iwlmvm uses it) and
the implementation is also broken for MLO.

Remove the flag in favour of calling drv_mgd_prepare_tx() without
any conditions even for the deauth-while-assoc case. The drivers
that implement it can take the appropriate actions, which for the
only user of DEAUTH_NEED_MGD_TX_PREP (iwlmvm) is a bit more tricky
than the implementation in mac80211 is anyway, and all others have
no need and can just exit if info->was_assoc is set.

Reviewed-by: Miriam Rachel Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20240627132527.94924bcc9c9e.I328a219e45f2e2724cd52e75bb9feee3bf21a463@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>