samples: dfu: add log for different release number

[szczys]

Add message when a release number is received from Golioth that doesn't match what is currently running. This indicates an OTA firmware update should be performed (it will either be an update or a rollback). This change compliments the message we log when the received semantic version matches what is currently running on the device.

[github-actions[bot]]

Visit the preview URL for this PR (updated for commit 6b5567f):

https://golioth-zephyr-sdk-doxygen-dev--pr451-szczys-add-dfu-n-yeyb4ff5.web.app

_{(expires Mon, 15 Jan 2024 20:06:34 GMT)}

_{🔥 via Firebase Hosting GitHub Action 🌎}

_{Sign: a389eefadf4b4b68a539327b3459dd66c142cf49}