This is part 2 of the fix. The tool that extracts the nuttx
   git tag was broken by a new tag added the did not match
   the form nuttx-M.mm. To the value was printed as

   OS: NuttX
   OS version: 0.0.0 c0 (192)

  Once that issue was fixed, it was apparent that recent
  changes to version.c return the values as base 10, before
  it was hex. This fixes the formatting.

  This is part one of a fix for cascading failure. The NuttX
  nuttx repos was tagged with upstream_7.18+ and broke the tag
  extraction that was expecting nuttx-M.mm

previously, get_devname() was used as the I2C device path, but on NuttX,
get_devname() is the device file which the driver creates. This patch
changes it, so the sematics are the same as on NuttX: both now use _bus
to decide to which I2C bus device to talk to.

I did not see any other use-cases than the led on ocpoc.

This is already added to the global list, and we already removed this
flag previously, but some of them sneaked back in.

2. Remove printf in the cpp

Add -D__DF_RPI in posix_rpi_common.cmake
Add rpi_rc_in and rpi_pca9685_pwm_out  driver in posix_rpi_common.cmake
Rename posix_rpi_cross_without_navio_or_pxfmini to posix_rpi_cross_no_shield.cmake

2. Rewrite and rebase pca9685 driver
3. Try to fix issue when push the stick of channel 3 to the maxmum position, 0uswill be output to channel 1, should be maxmum pwm signal
4. Fix the code style

Now I've fixed style of the code

Both 8 channels PPM encoder and 8 channels revicer are required.
Before launch px4, ppmdeocde programe should be launched.
To download ppmdecode programe,
visit https://github.com/crossa/raspberry-pi-px4firmware.
Pxfmini and navio are not popular autopilot hardware in china,
I can handly to purchase it.
So that I use raspberry pi to build autopilot separately.
This dirver help us to decode ppm single to pwm and pushlish it

Just update in RAM is enough.

Use the size of each item type instead of the biggest one.

In AeroFC that runs is constrained mode it was using 7860 bytes
and now it uses 6930 bytes almost 1KB less.