Bluetooth: Rename extfeatures

This patch renames hdev->extfeatures to hdev->host_features since it
holds the extended features Page 1 (aka host features).

Signed-off-by: Andre Guedes <aguedespe@gmail.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>