* stm32f407: add Uart support
* lpc1768: add cpu_frequency in board and chip
Allow using them with microzig Uart, which ensures the clock is present
* lpc1768: fix UART2 and UART3 peripheral clock register
They are in the PCLKSEL1 register, not PCLKSEL0
* uart-sync: use native microzig Uart, target different boards/chips
The previous example was lpc1768 specific, this new example should work with all
board and chips which implement the microzig Uart functionality. Instead of 4
LEDs, the new example uses a single LED to provide minimal debugging
capabilities if something does not work correctly.
This allows building this example for the stm32 f3 and f4 discovery boards.
Matheus C. França
Riccardo Binetti
Felix Queißner
Matt Knight
Vesim