Bluetooth: Fix checks for LE support on LE-only controllers

LE-only controllers do not support extended features so any kind of host
feature bit checks do not make sense for them. This patch fixes code
used for both single-mode (LE-only) and dual-mode (BR/EDR/LE) to use the
HCI_LE_ENABLED flag instead of the "Host LE supported" feature bit for
LE support tests.

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>
Signed-off-by: John W. Linville <linville@tuxdriver.com>