Revert "tL2C_TX_COMPLETE_CB_INFO is unused"

This reverts commit f6e5ab49.

The assumption in the original CL "L2cap tx completes immediately"
seems to be incorrect.

Bug: 314819704
Bug: 301168932
Test: m -j

Change-Id: I8460822b9cb6bc48045f8cf15c3e587507be5741