Navio: RC Input prototype code and fixes

Ublox SPI stub solves bad WHOAMI issue with MPU9250 as it happens because Ublox CS could be active before running APM.
SPI mode changed for MPU9250 to SPI_MODE_0 to resolve conflict with Ublox as it does not work in SPI_MODE_3. 
RCInput code is a quick prototype that uses pigpio daemon to sample RCInput pulses.
Types in GPIO_RPI changed to stdint, printfs changed to hal.scheduler->panic("").
Fixed incorrect GPIO read, that was causing simultaneous chip select warnings.