AP_InertialSensor_MPU6000: Remove MPU6000_CS_PIN

Remove MPU6000_CS_PIN, a legacy way of handling
Chip Select.
AP_InertialSensor_MPU9250.cpp: Update the DRDY pin.
AP_InertialSensor_MPU9250: remove legacy CS.
HAL_Linux: change to mem access method from sysfs access method

This step is taken to reduce the time for gpio access substantially
HAL_Linux: spidev1.0 to SPI0 and spidev2.0 to SPI1
AP_InertialSensor_MPU9250: Add missing library for example/

In order to compile the examples test a library needed to
added.
Tools: Add PXF enable and check CS scripts
AP_InertialSensor: Add missing library to test example.
HAL_Linux: Add CS capabilities to the SPI driver.
AP_InertialSensor_MPU9250: Fix SPI CS.
AP_InertialSensor_MPU6000: Fix the CS.
AP_InertialSensor_LSM9DS0: Fix the CS.
AP_Baro_MS5611_test: Add block for APM2-code
AP_Motors:add AP_Motors_Time_test
HAL_Linux: make GPIO code compact and readable

add hal instance to generate scheduler
change gpio/export write method
add gpio struct to LinuxDigitalSource class
change individual gpio banks to one gpio_bank array
HAL_Linux: add HAL_ prefix to GPIO_INPUT
AP_Baro_MS5611_test: Add HAL specific code.
HAL_Linux: BUS_SPEED selected individually in SPIDriver
HAL_Linux: Make the CS variables more readable in SPIDriver
HAL_Linux: Improve error handling SPIDriver