staging: iio: isl29028: made alignment of variables in struct isl29028_chip consistent

The alignment of the variables in the struct isl29028_chip is not
consistent. This changes all of the variables to use consistent
alignment to improve the code readability.
Signed-off-by: Brian Masney <masneyb@onstation.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>