iio: ina2xx: Fix whitespace and re-order code

Group of probably overly rigorous whitespace and code cleanups.
 - Alphabetize includes
 - Assign to variables in the order they are defined
 - Alignment issues
 - Group alike statements together
 - Use helper macros

Signed-off-by: Andrew F. Davis <afd@ti.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>