samples: drivers: watchdog: Update sample to use alias
samples: drivers: watchdog: Update sample to use alias

Simplify sample by using DT_ALIAS to make the sample more generic.

Signed-off-by: Benjamin Björnsson <8044ef148b03b50e606a03e6e88e2c21cb9a92a8@gmail.com>

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