L2CAP: Handle invalid HCI packets

- Handled Buffer over flow for uint16_t
- Discard invalid HCI packets from Codenomican test
  tool as data length and actual data not matching
  during reassembly

Use case:
Execute L2CAP test suit from Defensics Codenomican

Steps:
1. Pair and connect DUT to Codenomican tool
2. Execute L2CAP test suit from Defensics Codenomican

Failure:
Crash observed on DUT and Codenomican tool stuck in execution.

Root cause:
Codenomican tool sending invalid HCI packets to DUT and
there are no checks to handle buffer over flow and other invalid data
from Codenomican tool.

Bug: 29498064
Change-Id: I6f93c80244fc39d607ad285185136bbbca83d7ae