Fix no data issue after system server crash

FW was checking "Radio Available" instead of "Radio On" when
broadcasting data availability. This was causing an issue in
a certain recovery case (system server restart/phone process
restart) where "Radio (modem) is available" but radio was
turned off.

This patch obsolete the use of mRadioAvailable attribute and
use RadioState from RIL directly to check if Radio is ON.

Bug:5077346
Change-Id: Ie7ac05e3d5e328e3d5303541ca41326754f309c1