gpssim: don't advertize uninitialized data
gpssim: don't advertize uninitialized data

According to valgrind uninitialized bytes were being advertized.

PX4/Firmware,krbeverx/Firmware,acfloria/Firmware,dagar/Firmware,acfloria/Firmware,PX4/Firmware,dagar/Firmware,krbeverx/Firmware,acfloria/Firmware,dagar/Firmware,dagar/Firmware,PX4/Firmware,krbeverx/Firmware,PX4/Firmware,acfloria/Firmware,PX4/Firmware,krbeverx/Firmware,PX4/Firmware,dagar/Firmware,acfloria/Firmware,acfloria/Firmware,krbeverx/Firmware,PX4/Firmware,acfloria/Firmware,krbeverx/Firmware,dagar/Firmware,dagar/Firmware,krbeverx/Firmware