Use hardware timer and binary semaphore to control precice duration
This commit still have not done verify yet. In this commit, I did
1)use this method to keep the frequency of flight control task be 4kHz
2)disable tim10(we do not use it now, prevent some isr issues)
3)use led 2 to debug timer interrupt
Modify the mpu9250 calibration data to fboris's version
Merge branch 'fix_flight_control_freq' of https://github.com/fboris/firmware into os_dev
Enable the ground station communication task
Merge branch 'fix_flight_control_freq' into os_shengwen_flight
Calibrate the magnetometer