Flight/F1 ADC- Refactor F1 ADC driver to use a two stage aproach

This abstracts the upper driver from the type of ADC device used
(internal, external).
Flight/ADC - Modified att and sys modules to work with refactored driver

Make use of the new upper driver functions on the attitude
and systemmod modules.
Flight/ADC - Created a new PCF8591(8x8bit adc)  driver

This is to be used with the two stage driver aproach
as a lower driver.
Flight/ADC - F1 Internal and PCF8591 bugfixes

Use NULL instead of -1 on internal driver.
Fix device validation function usage on pcf driver.
Flight/Battery Module - Convert the timer callback into a task

Refactor the battery module into a task instead of the previous timer
callback
This was needed because using a timer callback was triggering the WDG
when using an external I2C ADC.
Flight/ADC - Changed CC makefile to handle the new PCF8591 driver
Flight/ADC-Upper driver-Conditional compilation of function using freertos defined type.

It was breaking CC Bootloader compilation
Flight/ADC -Made several functions private, fixed code style

Changes acording to review coments.
This afected upper ADC driver, lower internal ADC driver
and PCF8591 lower ADC driver.
Flight/F1 ADC - Removed unused functions from the F1 internal ADC driver
Flight/F1 ADC -Internal driver, made 2 functions private

These functions are now accessed trough upper driver API
Flight/F3 ADC-Start of F3 ADC driver and of DMA interrupt subscribing functions.

WIP
Flight/DMA-Changed interrupt subscription functions to support up to 3 subscribers
Flight/F3 ADC-Enabled lower internal adc driver for testing
Flight/F3 ADC-Added new functions to the driver

Tested with master only, 1 and 2 channels.
Flight/F3 ADC-Several changes, tested in single and dual mode.
Flight/F3 ADC-Made the driver work without FREERTOS.
Flight/F3 ADC -Refactored to use 2 layer driver system.

Added some documentation
Flight/ADC-Fixed CC compile, made changes to the DMA interrupt subscribing functions.
Flight/F3 ADC-Added ADC example configuration to board_hw_defs

Added configuration for F3 ADC to be used for testing.
Current configuration uses single mode ADC, uncomment commented lines
and comment related ones to test dual mode.
Flight/F4 ADC-Refactor to dual layer driver style