l2c: Fix CoC default response

Looks like patch:
9a6e043d Restore LE CoC l2cap conn rsp

was merged in similar time that:
648dd98e stack/l2c: Add support for credit based connection oriented channels

However those two have a conflict.
This patch fixes that.

Tag: #feature
Bug: 159786353
Sponsor: jpawlowski@
Test: compile & manual
Change-Id: Ie252d15bdad9d20d9006908aa34e8b566583e4be