Bluetooth: Use ERR_PTR as return error from hci_connect

Use ERR_PTR mechanism to return error from hci_connect.

Signed-off-by: Ville Tervo <ville.tervo@nokia.com>
Signed-off-by: Anderson Briglia <anderson.briglia@openbossa.org>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>