gpio: pca953x: remove redundant assignments

There are few redundant assignments of ret variable which is updated anyway.
Remove them for good.

While here, correct indentation of the constant definition and remove one empty
line.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>