iio: imu: inv_mpu6050: Remove duplicate NULL check

Since i2c_unregister_device() became NULL-aware we may remove duplicate
NULL check.

Cc: Jonathan Cameron <jic23@kernel.org>
Cc: Hartmut Knaack <knaack.h@gmx.de>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Peter Meerwald-Stadler <pmeerw@pmeerw.net>
Cc: linux-iio@vger.kernel.org
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/imu/inv_mpu6050/inv_mpu_acpi.c

@@ -196,7 +196,6 @@ void inv_mpu_acpi_delete_mux_client(struct i2c_client *client)
 {
 	struct inv_mpu6050_state *st = iio_priv(dev_get_drvdata(&client->dev));
 
-	if (st->mux_client)
 	i2c_unregister_device(st->mux_client);
 }
 #else