Bluetooth: Add initial support for LE-only controllers

This patch splits off most the HCI init sequence commands from a fixed
set into a conditional one that is sent once the HCI_Read_Local_Features
and HCI_Read_Local_Version_Information commands complete. This is
necessary since many of the current fixed commands are not allowed for
LE-only controllers.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>