Drivers: iio:adc: fix brace coding style issue in at91_adc.c

This is a patch to the at91_adc.c file that fixes up a brace
warning found by the checkpatch.pl tool

Signed-off-by: Venkat Prashanth B U <venkat.prashanth2498@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>