Remove unused send_eapol() driver op

Remove unused send_eapol() driver op

The send_eapol() callback was used by driver_test.c, but with that
removed, there is no remaining users of the alternative EAPOL frame
transmitting mechanism in wpa_supplicant, i.e., all remaining driver
interfaces use l2_packet instead. Remove the send_eapol() to get rid of
unused code.

Signed-off-by: Jouni Malinen <j@w1.fi>