gpio: pca953x: remove incorrect le16_to_cpu calls

i2c_smbus commands handle the correct byte order for smbus transactions
internally. This will currently result in incorrect operation on big
endian systems.

Suggested-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>