Instead of going through 'hal' then 'scheduler', use directly the AP_HAL
functions. Besides removing indirection that is not necessary for such
functions, this patch ends up reducing the code size in the call sites.
For example, building ArduCopter for PX4 with this change (compared to
before introduction of the functions) yields almost 3k bytes of code
size.
# ArduCopter build before the functions (1b29a1af46)
text data bss dec hex filename
895264 2812 62732 960808 ea928 /.../px4fmu-v2_APM.build/firmware.elf
# ArduCopter build after this patch
text data bss dec hex filename
892264 2812 62732 957808 e9d70 /.../px4fmu-v2_APM.build/firmware.elf
A later patch will remove the unused functions in the Schedulers.
ee073787c8