Merge changes Id5c2d642,I288816ab,If435eb75,I5c0c796d,I5c1b442a

* changes:
  Clean up bta_dm_pm_set_sniff_policy
  Rename set/clear policy, since it's just about role switch
  Remove bta_sys_clear_policy -> direct call
  Remove bta_sys_set_policy -> direct call
  HCI_ENABLE_SNIFF_MODE is never removed