net: lwm2m: Add API function to delete object instance

Since the API already has a function to create an LwM2M object instance,
it makes sense to add a corresponding delete funtion, allowing the
application to delete created objects.

Additionally, for the remote delete set the Registration Update trigger
only when not in bootstrap mode.

Signed-off-by: Robert Lubos <robert.lubos@nordicsemi.no>
3 files changed