* Made voxl2 apps processor and slpi dsp processor builds into separate board builds so that they can
more easily be configured independently.
* Removed board specific link library command from px4_config.cmake and moved it to a more generic
board specific solution that can be used by any board that needs custom link libraries.
* Removed redundant cmake command for Qurt
* Removed unused definition from Qurt cmake file
* Removed unnecessary QURT_LIB cmake function
* Reorganized the voxl2 build structure to avoid 4 level board directories.
* Reverted cmake files to remove 4 level board naming code
* Updated documentation
The bulk of this change was tightly coupled and needed to be deleted in one pass. Some of the smaller changes were things that broke as a result of the initial purge and subsequently fixed by further eradicating unnecessary platform differences. Finally, I deleted any dead code I came across in the related files I touched while going through everything.
- DriverFramework (src/lib/DriverFramework submodule) completely removed
- added dspal submodule in qurt platform (was brought in via DriverFramework)
- all df wrapper drivers removed
- all boards using df wrapper drivers updated to use in tree equivalents
- unused empty arch/board.h on posix and qurt removed
- unused IOCTLs removed (pub block, priv, etc)
- Integrator delete methods only used from df wrapper drivers
- commander: sensor calibration use "NuttX version" everywhere for now
- sensors: update to px4_{open, read, close} instead of DevMgr wrapper (adc open for analog differential pressure)
- battery_status: update to px4_{open, read, close} instead of DevMgr wrapper (adc open for analog differential pressure)
- cdev cleanup conflicting typedefs and names with actual OS (pollevent_t, etc)
- load_mon and top remove from linux boards (unused)
- delete unused PX4_MAIN_FUNCTION
- delete unused getreg32 macro
- delete unused SIOCDEVPRIVATE define
- named each platform tasks consistently
- posix list_devices and list_topics removed (list_files now shows all virtual files)
- fixed df_ltc2946_wrapper battery dependency
- fixed px4::atomic fetch_add for QuRT
- updated PX4 QuRT SPI wrapper to set bus frequency
- renamed "qurt-default" configs to just "qurt"
