AP_InertialSensor: disable reset on MPU9250

The Compass library is initialized before the InertialSensor. AK8963 with
MPU9250 as backend already takes care of resetting MPU9250. The problem with
also resetting it in the MPU9250 initialization code is that if the reset
happens during an internal I2C transaction, the AK8963 may hang. So here we
remove the reset inside MPU9250. There still a possibility that the first
MPU9250 initialization is not successful and it resets the chip, but it's not
happening in tests.

libraries/AP_InertialSensor/AP_InertialSensor_MPU9250.cpp

@@ -417,11 +417,6 @@ bool AP_InertialSensor_MPU9250::_hardware_init(void)
     // Chip reset
     uint8_t tries;
     for (tries = 0; tries<5; tries++) {
-        // reset device
-        _register_write(MPUREG_PWR_MGMT_1, BIT_PWR_MGMT_1_DEVICE_RESET);
-
-        hal.scheduler->delay(100);
-
         // disable I2C as recommended by the datasheet
         _register_write(MPUREG_USER_CTRL, BIT_USER_CTRL_I2C_IF_DIS);