wifi: brcmfmac: add per-vendor feature detection callback

Adding a .feat_attach() callback allowing per-vendor overrides
of the driver feature flags. In this patch the callback is only
provided by BCA vendor to disable SAE feature as it has not been
confirmed yet. BCA chips generally do not have the in-driver
supplicant (idsup) feature so they rely on NL80211_CMD_EXTERNAL_AUTH
to trigger user-space authentication.

Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://msgid.link/20240103095704.135651-3-arend.vanspriel@broadcom.com