Introduce pL2CA_Error_Cb

L2CAP notifies users error in ConnectRsp and ConfigRsp through this
callback function (not linked so far). Next step is we send success
through pL2CA_ConnectCfm_Cb and pL2CA_ConfigCfm_Cb.

Bug: 159815595
Tag: #refactor
Test: compile & verify basic functions working
Change-Id: I4456487d36248408fc1c31403d107baef05e3646