verification/dot2c: Remove superfluous enum assignment and add last comma

verification/dot2c: Remove superfluous enum assignment and add last comma

The header files generated by dot2c currently create enums for states
and events assigning the first element to 0. This is superfluous as it
happens automatically if no value is specified.
Also it doesn't add a comma to the last enum elements, which slightly
complicates the diff if states or events are added.

Remove the assignment to 0 and add a comma to last elements, this
simplifies the logic for the code generator.

Reviewed-by: Nam Cao <namcao@linutronix.de>
Link: https://lore.kernel.org/r/20251126104241.291258-8-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>