Fix L2CAP exceed max transmit for both I-frame and S-frame under ERTM

Fix L2CAP exceed max transmit for both I-frame and S-frame under ERTM

* Under ERTM mode, ReqSeq of S-frame with R-bit set to RR is used to
  acknowledge previously received I-frames numbered up to and including
  ReqSeq - 1. So valid ReqSeq is start from 1.
* Stack should not retransmit I-frame once it exceed max transmittion
  and initiates closure of the L2CAP channel.
* Add following tests in simple_l2cap_test:
    test_i_frame_transmissions_exceed_max_transmit

Bug: 148771210
Test: run_cert.sh

Change-Id: Id1fb2fab8be7f7e05a09935002366e60df5f7b81