iio: magn: bmc150_magn: add locking comment for runtime resume

Runtime resume function is called with the data->mutex lock held.
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Signed-off-by: Irina Tirdea <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/magnetometer/bmc150_magn.c

···
 	return 0;
 }
 
+/*
+ * Should be called with data->mutex held.
+ */
 static int bmc150_magn_runtime_resume(struct device *dev)
 {
 	struct iio_dev *indio_dev = i2c_get_clientdata(to_i2c_client(dev));