tests: drivers: can: api: define DT_CAN_1_NAME if not defined
tests: drivers: can: api: define DT_CAN_1_NAME if not defined

Define DT_CAN_1_NAME as an empty string if it is not defined.
This is useful for buildtest where no HW is available.

Signed-off-by: Alexander Wachter <ce6e77dabd455f5e273537afd862be63bdedff84@student.tugraz.at>

Vudentz/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,finikorg/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,nashif/zephyr,nashif/zephyr,Vudentz/zephyr,galak/zephyr,finikorg/zephyr,galak/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,GiulianoFranchetto/zephyr,GiulianoFranchetto/zephyr,galak/zephyr