microbit: BUGFIX - Input validation in MicroBitDisplay::setBrightness()
microbit: BUGFIX - Input validation in MicroBitDisplay::setBrightness()

Updates to MicroBitDisplay::setBrightness() to perform a NOP for out of bound parameters.
This aligns the functionality of the runtime with the TD simulator.

markshannon/microbit-dal,markshannon/microbit-dal