iio: imu: inv_mpu6050: Drop double check for ACPI companion device

acpi_dev_get_resources() does perform the NULL pointer check against
ACPI companion device which is given as function parameter. Thus,
there is no need to duplicate this check in the caller.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>