drivers: can: mcan: sjw not initialized when CAN_FD_MODE is enabled

[str4t0m]

Describe the bug
The mcan driver does not initialize the timing.sjw variable in CAN_FD_MODE configuration.
This causes undefined behavior and might trigger a assert that checks the valid range of this parameter.

Expected behavior
The synchronization jump width should be initialized with the parameter configured.

Impact
Undefined behavior might lead to synchronization problems.

[alexanderwachter]

Fix: #35738