delete unused IOCTL ACCELIOCGEXTERNAL

src/drivers/drv_accel.h

src/drivers/imu/mpu6000/mpu6000.cpp

src/drivers/imu/mpu6000/mpu6000_i2c.cpp

src/drivers/imu/mpu6000/mpu6000_spi.cpp

src/drivers/imu/mpu9250/mag_i2c.cpp

src/drivers/imu/mpu9250/mpu9250.h

src/drivers/imu/mpu9250/mpu9250_i2c.cpp

src/drivers/imu/mpu9250/mpu9250_spi.cpp