This commit ensures all architectures do the proper things to work
with either end-to-end and peer-to-peer, and all frames use the
proper addresses

 * we avoid ifdef by using HAS_PTP and HAS_E2E
 * no need to -D config items in Makefile
 * wrpc now correctly sets ppg->delay_mech at startup
 * the simulator now correctly sets ppg->delay_mech at startup
 * bare archs correctly set ppg->delay_mech at startup
 * bare archs properly use one or the other multicast address
 * pp_instance_cfg->delay_mech is removed as not yet used

Signed-off-by: Alessandro Rubini <rubini@gnudd.com>