mpu6000: added -X option for external bus
mpu6000: added -X option for external bus

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