Made cc2420 follow the same logic as cc2538 when
disabling the unmodulated carrier. Now they both
return to the state they were in before the carrier
was enabled.
Modified the cc2420 driver to enable the radio test
mode to emit unmodulated carriers (tones).
A carrier can be enabled using the normal radio driver
API:
NETSTACK_CONF_RADIO.set_value(
RADIO_PARAM_POWER_MODE,
RADIO_POWER_MODE_CARRIER_ON);
Once enabled, the carrier can be disabled like this:
NETSTACK_CONF_RADIO.set_value(
RADIO_PARAM_POWER_MODE,
RADIO_POWER_MODE_CARRIER_OFF);
