Bluetooth: Resume advertising after LE connection

When an LE connection request is made, advertising is disabled and never
resumed. When a client has an active advertisement, this is disruptive.
This change adds resume logic for client-configured (non-directed)
advertisements after the connection attempt.

The patch was tested by registering an advertisement, initiating an LE
connection from a remote peer, and verifying that the advertisement is
re-activated after the connection is established. This is performed on
Hatch and Kukui Chromebooks.

Signed-off-by: Daniel Winkler <danielwinkler@google.com>
Reviewed-by: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>