gpio: pca953x: Drop unused fields in struct pca953x_platform_data

[ Upstream commit 2f4d3e29 ]

New code should solely use firmware nodes for the specifics and
not any callbacks.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Stable-dep-of: 7cef813a ("gpio: pca953x: log an error when failing to get the reset GPIO")
Signed-off-by: Sasha Levin <sashal@kernel.org>