wifi: nl80211: force WLAN_AKM_SUITE_SAE in big endian in NL80211_CMD_EXTERNAL_AUTH

User-space supplicant (observed at least on wpa_supplicant) historically
parses the NL80211_ATTR_AKM_SUITES from the NL80211_CMD_EXTERNAL_AUTH
message as big endian _only_ when its value is WLAN_AKM_SUITE_SAE, while
processing anything else in host endian. This behavior makes any driver
relying on SAE external auth to switch AKM suite to big endian if it is
WLAN_AKM_SUITE_SAE. A fix bringing compatibility with both endianness
has been brought into wpa_supplicant, however we must keep compatibility
with older versions, while trying to reduce the occurences of this manual
conversion in wireless drivers.

Add the be32 conversion specifically on WLAN_AKM_SUITE_SAE in nl80211 layer
to keep compatibility with older wpa_supplicant versions.

Suggested-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Alexis Lothoré <alexis.lothore@bootlin.com>
Link: https://msgid.link/20240215-nl80211_fix_akm_suites_endianness-v1-1-57e902632f9d@bootlin.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>