Bluetooth: Introduce HCI_ADVERTISING_INSTANCE setting and add AD flags

This patch introduces the HCI_ADVERTISING_INSTANCE setting, which is set
when an at least one advertising instance has been added using the
"Add Advertising" mgmt command. This patch also adds a macro definition
for the EIR_APPEARANCE field type.

Signed-off-by: Arman Uguray <armansito@chromium.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>