mk: refactor platforms for different fmu variants
ivory-bsp-stm32f4: support fmu bare or with ioar
ivory-px4-hw: refactor ioar driver, test

test is now called is copter-motor-test
empty driver for supporting bare px4fmu
app build: copter-motor-test renamed from px4ioar-hw-test
flight: app imports px4ioar motor controller explicitly
ivory-bsp-stm32f4: register defs for General Purpose Timer