The argument in init() is not used by any implementation. Add a second
method without it so the HAL implementation can used it instead. Later
the unused method will be removed.
Add a deinit() counterpart. This is needed for some ports that require some deinitializtion logic. The default implementation is empty. I'm not sure whether we need to inforce it for all.
this makes calling new_input() in RCInput clear the new input
flag. This fixes an issue with calls to read() for auxillary channels
clearing the new_input flag, which could cause brief failsafe
conditions.