CC1120 driver tweaks
Changed CC1120 driver to use MCU_WAKEUP instead of previous interrupt source.
CC1120 driver tweaks.
CC1120 driver tweaks.

Bugfix for Contikimac where padding is not actually happeneing on short packets.
Merge branch 'release-2-7' of https://github.com/feshie/contiki into release-2-7