Bluetooth: Call l2cap_le_conn_ready after notifying channels

For most cases it makes no difference whether l2cap_le_conn_ready() is
called before or after calling the channel ready() callbacks, however
for upcoming SMP code we need this as the ready() callback initializes
certain structures that a call to smp_conn_security() from
l2cap_le_conn_ready() depends on. Therefore, move the call to
l2cap_le_conn_ready() after iterating through and notifying channels.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>