canbus: canopen: add program download support

Add program download (firmware update) support according to the CAN in
Automation (CiA) 302-3 draft standard proposal v4.1.0.

The implementation supports a Zephyr specific vendor command allowing
external confirmation of a newly booted firmware image. If this is not
desired, the application can confirm the image by other means.

Signed-off-by: Henrik Brix Andersen <hebad@vestas.com>