Bluetooth: mgmt: Fix enabling SSP while powered off

Bluetooth: mgmt: Fix enabling SSP while powered off

When new BT USB adapter is plugged in it's configured while still being powered
off (HCI_AUTO_OFF flag is set), thus Set SSP will only set dev_flags but won't
write changes to controller. As a result remote devices won't use Secure Simple
Pairing with our device due to SSP Host Support flag disabled in extended
features and may also reject SSP attempt from our side (with possible fallback
to legacy pairing).

This patch ensures HCI Write Simple Pairing Mode is sent when Set Powered is
called to power on controller and clear HCI_AUTO_OFF flag.

Signed-off-by: Andrzej Kaczmarek <andrzej.kaczmarek@tieto.com>
Cc: stable@vger.kernel.org
Acked-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>