iio: adc: at91: make the function handle_adc_eoc_trigger() static

The handle_adc_eoc_trigger() in only used in at91_adc.c. So make it
static.
Signed-off-by: Josh Wu <josh.wu@atmel.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/adc/at91_adc.c

@@ -266,7 +266,7 @@ static irqreturn_t at91_adc_trigger_handler(int irq, void *p)
 }
 
 /* Handler for classic adc channel eoc trigger */
-void handle_adc_eoc_trigger(int irq, struct iio_dev *idev)
+static void handle_adc_eoc_trigger(int irq, struct iio_dev *idev)
 {
 	struct at91_adc_state *st = iio_priv(idev);