iio: Avoid multiple line dereference for mask

Prefer lines > 80 characters over splitting dereferences across multiple
lines. Reported by checkpatch.pl.

Signed-off-by: Joe Simmons-Talbott <joetalbott@gmail.com>
Link: https://lore.kernel.org/r/20220819182012.219523-1-joetalbott@gmail.com


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