staging: iio: Remove unnecessary externs

Using 'extern' is not necessary for function prototypes.
Signed-off-by: NJoe Perches <joe@perches.com>
Acked-by: NLars-Peter Clausen <lars@metafoo.de>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/iio/meter/ade7854.h

@@ -168,7 +168,7 @@ struct ade7854_state {
 
 };
 
-extern int ade7854_probe(struct iio_dev *indio_dev, struct device *dev);
-extern int ade7854_remove(struct iio_dev *indio_dev);
+int ade7854_probe(struct iio_dev *indio_dev, struct device *dev);
+int ade7854_remove(struct iio_dev *indio_dev);
 
 #endif