wifi: mac80211: don't require cipher and keylen in gtk rekey

ieee80211_add_gtk_rekey receives a keyconf as an argument, and the
cipher and keylen are taken from there to the new allocated key.
But in rekey, both the cipher and the keylen should be the same as of
the old key, so let ieee80211_add_gtk_rekey find those, so drivers won't
have to fill it in.

Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20250721214922.3c5c023bfae9.Ie6594ae2b4b6d5b3d536e642b349046ebfce7a5d@changeid


Signed-off-by: Johannes Berg <johannes.berg@intel.com>