staging: iio: isl29018: fix multiline comment syntax

Change multiline comments from:

/* line1
 * line2
 * ...
 */

to

/*
 * line1
 * line2
 * ...
 */

Signed-off-by: Brian Masney <masneyb@onstation.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>