Many simple kconfig configurations are added to boards and brought in with the board name.
This makes a common import of these configs so one only requires adding a BOARD.config without having to alter the makefile.
The boards/stm32f429i-disco board is an ealier version of the stm32f429i-disc1.
The boards are compatible with the difference that the older on-board debugger
does not provide a UART connection.
To spare the user of having to wire up a USB-TTL adapter, enable CDC-ACM
on the micro-USB port.