Merge changes I0aa05e5b,I4c2bc679,I2b0a15e8,I8aabfbc4,Ifc8114d9, ...

* changes:
  Remove unused code in rfc_int.h
  Remove sec_id related code in RFCOMM
  Move rfcomm security requirement to rfcomm module
  Clear RFCOMM security when done
  Get rid of p_cur_service in dev_rec
  Legacy RFCOMM: Use the new security record
  Introduce BTM_SetRfcommSecurity