gpio: pca953x: avoid logically dead code

The current code logic make the condition "else if (reg >= 0x54)"
can't be true, cause the dead code. So fix it to match the coder
expectation. This is reported by Coverity.

Fixes: 13c5d4ce

 ("gpio: pca953x: Add support for PCAL6534")
Signed-off-by: Haibo Chen <haibo.chen@nxp.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>