gpio: pca953x: coding style fixes

pca953x_gpio_set_multiple() has some coding style issues that make it
harder to read. Tweak the code a bit.

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