iio: adc: at91_adc: Fix 'bad line' warning

All lines should start with ' *'.

Fixes the following W=1 kernel build warning(s):

 drivers/iio/adc/at91_adc.c:160: warning: bad line:                         (Interruptions registers mostly)

Cc: Nicolas Ferre <nicolas.ferre@microchip.com>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Ludovic Desroches <ludovic.desroches@microchip.com>
Cc: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/at91_adc.c

@@ -157,7 +157,7 @@
  * struct at91_adc_reg_desc - Various informations relative to registers
  * @channel_base:	Base offset for the channel data registers
  * @drdy_mask:		Mask of the DRDY field in the relevant registers
-			(Interruptions registers mostly)
+ *			(Interruptions registers mostly)
  * @status_register:	Offset of the Interrupt Status Register
  * @trigger_register:	Offset of the Trigger setup register
  * @mr_prescal_mask:	Mask of the PRESCAL field in the adc MR register