proto_80211_mac_hdr: Don't use C99 for-loop variable initialization

Stay consistent with coding style.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
proto_ip_authentication_hdr: Don't use C99 for-loop variable initialization

Stay consistent with coding style.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>