Support the following features:
 * Serial console on USART0.
 * Common pin configuration functions (needed for USART0).
 * Clock configuration: The Cortex-M4 core runs at 204 MHz.
 * `cptf` command is technically available, but has no effect since there is no
internal flash on LPC18x0/LPC43x0 MCUs.
 * The lowest SRAM region (128 KB at 0x10000000) is reserved for the currently
running U-Boot image.