Bluetooth: mgmt: Fix sending redundant event for Advertising Instance

When an Advertising Instance is removed, the Advertising Removed event
shouldn't be sent to the same socket that issued the Remove
Advertising command (it gets a command complete event instead). The
mgmt_advertising_removed() function already has a parameter for
skipping a specific socket, but there was no code to propagate the
right value to this parameter. This patch fixes the issue by making
sure the intermediate hci_req_clear_adv_instance() function gets the
socket pointer.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>