[4] is reserved for Flaps, so also having the tilt on it was preventing us from
using flaps on tiltrotors, and other ripple effects.
By using [8] the tilt is separated from all other channels - it requires to increase the size of
actuator_controls by 1 to 9.
Signed-off-by: Silvan Fuhrer <silvan@auterion.com>
This inversion matches the fixed sign in the commands generated
by the VTOL attitude controller.
This commit, combined with the previous commit, should have no effect.
For safety, it is recommended to check the direction of roll control
surfaces before flight.