Bluetooth: Remove missing code

This patch removes the struct adv_entry since it is not used anymore.
This struct should have been removed in commit 479453d5 (Bluetooth:
Remove advertising cache).

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>