hmc5883: add perf count, and removed unnecessary checks for -32768
hmc5883: add perf count, and removed unnecessary checks for -32768

we've already checked that the absolute value is <= 2048

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