gpio: xgene-sb: Remove unneeded definitions for properties

gpio: xgene-sb: Remove unneeded definitions for properties

There are three definitions for the property names. Remove them as:
1) each of them is only used once;
2) in all cases the definition is longer than the value.

In the result code is better and grepping on the property immediately
gets the function in which is being used which helps to guess the type
of the value.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20241018134550.2071101-2-andriy.shevchenko@linux.intel.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>