Bluetooth: Move EIR update to hci_request.c

We'll soon need to update the EIR both from hci_request.c and mgmt.c
so move update_eir() as a more generic request helper to
hci_request.c.

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