gpio: swnode: restore the name of the undefined software node

gpio: swnode: restore the name of the undefined software node

Commit 6774a66d0e10 ("gpio: swnode: compare the "undefined" swnode by
its address, not name") switched to comparing the software nodes by
address instead of names but it's still useful to keep the name of the
node to expose the relevant information over sysfs. Restore the
human-readable name.

Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Closes: https://lore.kernel.org/all/aVFsjSIwrBw7tFLU@smile.fi.intel.com/
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20260102093349.17822-1-bartosz.golaszewski@oss.qualcomm.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>