Bluetooth: L2CAP: Handle connection request

This handle connection request looking up for existing servers and
responding properly:

> ACL Data RX: Handle 3585 flags 0x02 dlen 18
      LE L2CAP: LE Connection Request (0x14) ident 1 len 10
        PSM: 128 (0x0080)
        Source CID: 64
        MTU: 672
        MPS: 230
        Credits: 10
< ACL Data TX: Handle 3585 flags 0x00 dlen 18
      LE L2CAP: LE Connection Response (0x15) ident 1 len 10
        Destination CID: 64
        MTU: 65
        MPS: 230
        Credits: 1
        Result: Connection successful (0x0000)

Change-Id: Ic0339518b80d9e38109f3efee6be4f0d2b084f1d
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>