stm32/led: Support an extra 2 LEDs in board configuration.
stm32/led: Support an extra 2 LEDs in board configuration.

Although the pyboard has only 4 LEDs, there are some boards that (may) have
more.  This commit adds 2 more LEDs to the led.c file that if defined in
the board-specific config file will be compiled in.

adafruit/circuitpython,adafruit/circuitpython,adafruit/circuitpython,adafruit/circuitpython,adafruit/circuitpython,adafruit/circuitpython