No activity on can_tx when running the ISO-TP sample

[abferm]

Describe the bug
No activity on can_tx when running the isotp sample.

To Reproduce
Steps to reproduce the behavior:

1. mkdir /tmp/isotp-bug && cd /tmp/isotp-bug
2. west init .
3. west update
4. cd zephyr
5. west build --pristine -b nucleo_f303re samples/subsys/canbus/isotp
6. sudo west flash
7. observe can_tx with oscilloscope

Expected behavior
Sample should function as described, and activity should be observable on the can_tx pin.

Impact
Sample intended to demonstrate setup and use of ISO-TP on the CAN bus does not correctly do so, making it difficult to determine how to use it in a real project.

Environment (please complete the following information):

• OS: Linux
• Toolchain: Docker Image zephyrprojectrtos/zephyr-build
• Version: v0.24.9-amd64

[henrikbrixandersen]

@abferm Thank you for reporting this. I have fixed it in #54137.