Add new board: Nucleo-F042K6

[Rigo-V]

Test setup: Nucleo-F042K6 wired to an EN25F80 (1024kB) on a breadboard. RESET/HOLD and WP pulled to VCC.

flashrom -p serprog:dev=/dev/serprog1,spispeed=36M -w rand 8,49s user 1,00s system 47% cpu 20,069 total

flashrom -p serprog:dev=/dev/serprog1,spispeed=36M -v rand 1,20s user 0,02s system 50% cpu 2,442 total

flashrom -p serprog:dev=/dev/serprog1,spispeed=36M -E 8,84s user 0,09s system 84% cpu 10,594 total