LinuxKPI: 802.11: fix field order in ieee80211_key_conf

[bz]

Summary

When adding the new field link_id to struct ieee80211_key_conf it
was erroneously placed at the of the struct; the zero-length (variable
sized) array for the key always needs to stay last.
Resort fields and add hopefully helpful comment to avoid the problem
in the future.

Fixes: adff403fe7a87
MFC after: 3 days

[cc]

Good catch!

Please correct the summary:

When adding the new field link_id to struct ieee80211_key_conf it
was erroneously placed at the of the struct;

to
When adding the new field link_id to struct ieee80211_key_conf, it
was erroneously placed at the end of the struct.