This fixes a race in `LED<NUM>_TOGGLE`, which is a read-copy-write
operation. Any access to a GPIO pin on the same GPIO port that
happens concurrently could result in data corruption. Using the
GPIO LL API, which is thread-safe, fixes the issue.
Note: The used GPIO LL functions will work even in when the GPIO LL
module is not used.
weact-f4xcx boards have only a single USB-C connector that is used for `highlevel_stdio` via USBUS CDC ACM so that it conflicts with tinyUSB for the moment.
Let boards only define the port and pin number of each LEDs. The common
definitions in `stm32_leds.h` will provide `LED<x>_ON`, `LED<x>_OFF`,
`LED<x>_TOGGLE`, `LED<x>_PIN`, `LED<x>_MASK` and `LED<x>_PORT`.
In addition to code de-duplication, this also makes it easier to use
LEDs in GPIO LL, which can be beneficial for super low overhead
debugging output - e.g. when a bug is timing sensitive and `DEBUG()`
would spent to much time for stdio to reproduce a bug.
This introduces KCONFIG_BOARD_CONFIG and KCONFIG_CPU_CONFIG variable for
boards and CPUs (including common directories) to add default
configuration files to be merged. The current approach, as it uses
Makefile.features, would include boards first, not allowing them to
override CPU configurations.
