Remove tL2C_CB::tL2C_LCB::p_hcit_rcv_acl

Never allocated, but always freed buffer

Luckily it's always null

Towards readable code

Bug: 163134718
Tag: #refactor
Test: compile & verify basic functions working
Change-Id: I0a5a6ea2178b1478b9a992028f5f181ed5344367