STDIO_UART_xx in peripheralnames.h
[DISCO_F429ZI] fix of RAM memory layout and stdio_uart

All test without any peripherals ("peripherals": []) are OK with these
two corrections.

- RAM start address was wrong - overlap with interrupt vector table
- wrong uart for stdio uart
Merge pull request #582 from ohagendorf/disco_f429zi

CMSIS/HAL: DISCO_F429ZI - correction of RAM memory layout in the linker script and stdio_uart config