Bluetooth: hci_ll: Convert to use h4_recv_buf helper

The HCILL or eHCILL protocol from TI is actually an H:4 protocol with a
few extra events and thus can also use the h4_recv_buf helper. Instead
of open coding the same funtionality add the extra events to the packet
description table and use h4_recv_buf.

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