Bluetooth: hci_uart: Provide generic H:4 receive framework

Future H:4 based UART drivers require custom packet types and custom
receive functions. To support this, extended the h4_recv_buf function
with a packet definition table.

For the default H:4 packets types of ACL data, SCO data and events,
provide helpers to reduce the amount of code duplication.

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