gpio: pca953x: correct type of reg_direction

The type of reg_direction needs to match the type of the regmap, which
is u8.

Fixes: 0f25fda8

 ("gpio: pca953x: Zap ad-hoc reg_direction cache")
Cc: Cc: <stable@vger.kernel.org>
Signed-off-by: David Jander <david@protonic.nl>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>