iio: adc: at91-sama5d2_adc: remove unneeded semicolon

A semicolon is not needed after a switch statement.

Signed-off-by: Tom Rix <trix@redhat.com>
Link: https://lore.kernel.org/r/20201027200853.1596699-1-trix@redhat.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>