HIDD: Use l2cap to enforce security

Instead of using btm_sec_mx_access_request() to enforce security, let
L2cap enforce security for us through btm_sec_l2cap_access_req().

Bug: 159815595
Tag: #refactor
Test: compile & verify basic functions working
Test: CtsVerifier HID
Change-Id: I89dd876228dd6ee9b25bc4fb024f2cd31288561d