fix "scripts: zephyr_flash_debug: flash like dfuutil.sh"

- When flashing with dfu-util while alt is not a number, the name must
  be quoted.

- Add missing commas in self.list_pattern

- Always call dfu-util with the VID/PID

Fixes: 257fa4af ("scripts: zephyr_flash_debug: flash like dfuutil.sh")
Signed-off-by: Marti Bolivar <marti.bolivar@linaro.org>