Add user configuration support to configure dot11 modes for
different vdev types.
Change-Id: I338d9d76f000195d1798bbc8b3b7ff1fb33ee305
CRs-Fixed: 2760240
Add dot11mode related cfg items in mlme cfg, and replace
old WNI dot11 modes with new MLME DOT11 mode enums
Change-Id: I6e866959f440ae781432c8aaa724b229c0874856
CRs-Fixed: 2362540