Reject L2CAP INFO RSP and ECHO RSP on the LE signaling channel

Steps:
Execute TC_LE_REJ_BI_02_C

Failure:
PTS stuck after sending INFO RSP, ECHO RSP on the LE signaling channel

Root Cause:
The Bluetooth stack is not rejecting INFO RSP, ECHO RSP even though
these commands are invalid for the LE signaling Channel.

Fix:
Reject the INFO RSP, ECHO RSP with error L2CAP_CMD_REJ_NOT_UNDERSTOOD.

Bug: 27852645
Change-Id: Ie09f658d606206cbdbea928e8cb6d10332743cf4
(cherry picked from commit d35bb40dd563e7f37df0a2fa9c0f61d0958b9601)