Add combo scan

Change-Id: Idd7c9fad10594da0ab21c51127cca271f27d3108
Add support for disable combo scan for wireless extension

If the combo scan isn't supported by wi-fi firmware, define this:

BoardConfig:
BOARD_WEXT_NO_COMBO_SCAN := true

Change-Id: Id06e097cbe500357c1ddec0a31ca8465822c4533