[BLUETOOTH]: l2cap info_timer delete fix in hci_conn_del

When the l2cap info_timer is active the info_state will be set to
L2CAP_INFO_FEAT_MASK_REQ_SENT, and it will be unset after the timer is
deleted or timeout triggered.

Here in l2cap_conn_del only call del_timer_sync when the info_state is
set to L2CAP_INFO_FEAT_MASK_REQ_SENT.

Signed-off-by: Dave Young <hidave.darkstar@gmail.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: David S. Miller <davem@davemloft.net>