tests: devicetree: device: Rename gpio@0 to avoid name conflict
tests: devicetree: device: Rename gpio@0 to avoid name conflict

There are some platforms like the lpcxpresso54114 that utilize gpio@0
so rename gpio@0 to gpio@ffff as this is a highly unlikely to conflict
with any real device.

Fixes #49439

Signed-off-by: Kumar Gala <383ef5577c6e1178b93f59ec8d0936f76d2a98c4@kernel.org>

galak/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,finikorg/zephyr,finikorg/zephyr