net: sockets: Add separate macro for registering offloaded sockets

Add a separate macro for registering offloaded sockets implementation,
along with information in the structure whether the implementation is
offloaded or not. This allows to differentiate between native and
offloaded socket implementations, which is critical for binding socket
API with an interface.

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