pwm_out_sim.cpp: fix initialization of _control_subs
pwm_out_sim.cpp: fix initialization of _control_subs

Note: {-1} initializes only the first element, and sets the others to 0.

PX4/Firmware,mcgill-robotics/Firmware,PX4/Firmware,PX4/Firmware,mcgill-robotics/Firmware,krbeverx/Firmware,PX4/Firmware,dagar/Firmware,krbeverx/Firmware,acfloria/Firmware,dagar/Firmware,Aerotenna/Firmware,darknight-007/Firmware,darknight-007/Firmware,mcgill-robotics/Firmware,mcgill-robotics/Firmware,jlecoeur/Firmware,mje-nz/PX4-Firmware,krbeverx/Firmware,acfloria/Firmware,jlecoeur/Firmware,dagar/Firmware,krbeverx/Firmware,krbeverx/Firmware,darknight-007/Firmware,mcgill-robotics/Firmware,PX4/Firmware,acfloria/Firmware,Aerotenna/Firmware,dagar/Firmware,acfloria/Firmware,mje-nz/PX4-Firmware,dagar/Firmware,dagar/Firmware,jlecoeur/Firmware,jlecoeur/Firmware,dagar/Firmware,Aerotenna/Firmware,krbeverx/Firmware,PX4/Firmware,krbeverx/Firmware,mje-nz/PX4-Firmware,jlecoeur/Firmware,mcgill-robotics/Firmware,jlecoeur/Firmware,mje-nz/PX4-Firmware,acfloria/Firmware,darknight-007/Firmware,darknight-007/Firmware,mje-nz/PX4-Firmware,mje-nz/PX4-Firmware,jlecoeur/Firmware,acfloria/Firmware,PX4/Firmware,Aerotenna/Firmware,Aerotenna/Firmware,jlecoeur/Firmware,mje-nz/PX4-Firmware,Aerotenna/Firmware,acfloria/Firmware,mcgill-robotics/Firmware,Aerotenna/Firmware