pwm: added -m option
pwm: added -m option

this allows setting of the channel mask directly, which is useful for
testing

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