iio: light: ltr501: Fix alignment to match open parenthesis

This makes ltr501 code consistent with the coding style adopted
for the new drivers added to IIO.
We prepare the path for adding support for LTR559 chip.

Reported by checkpatch.pl

Signed-off-by: Daniel Baluta <daniel.baluta@intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>