Lpc vic slot cleanup

Cleaned up the VIC slots... totally untested...
@dewagter @gautierhattenberger so please test!

See [arch/lpc21/vic_slots.txt](paparazzi/blob/e981f8047539e1eef18ea7e67e52c9b7a98d301d/sw/airborne/arch/lpc21/vic_slots.txt)

This should close #356