btm_proc_smp_cback: Don't access p_dev_rec if freed

In btm_proc_smp_cback(), return after p_dev_rec is freed in the middle
to prevent use after free

Bug: 120612744
Test: Use ASAN build; connect to a LE device and wait for timeout
Change-Id: Ic9d0eaeb62a1a1b24884146ca82f4104fabc5bac