A security fix to check buffer length in l2c_lcc_proc_pdu

Add check to make sure that data buffer is big enough to read the 2
bytes for length.

Bug: 120665616
Test: Run the SL4A Test for LE CoC, BleCoCTest
Change-Id: I30b7a8af11d3a5f974cb39e06b0e3463bebc8e9a