bluetooth: Initiate authentication before sending l2cap connect response.

Check and inititiate, if necessary, authentication procedure for
the connection before sending l2cap connect response. For legacy
devices, this patch will initiate authentication procedure in the
first l2cap connect request as legacy do not initiate authentication
after connection.

Change-Id: Ic788608452e8cac9e3eb1f71a2b63f671025d5f9
Signed-off-by: Kamal Negi <kamaln@codeaurora.org>
Signed-off-by: Rupesh Tatiya <rtatiya@codeaurora.org>