Modify the system time of Px4 flight control

1. stay platforms/nuttx/src/px4/stm/stm32_common/hrt/hrt.c Customize a time offset in the file , And added to the system time calculation .

2. stay src/drivers/drv_hrt.h The document states that .

 

 3. Declare again where you need to use .

 4. You can write the algorithm at your favorite position , modify abs_time_offset. This abs_time_offset Can affect the system time .