tuna: Add audio submix, enable WFD

Fixes Chromecast streaming!

Change-Id: Iae2ce082d45f91997b58df8284b25efb66aa67e4
Signed-off-by: Kyle Repinski <repinski23@gmail.com>

Conflicts:
	BoardConfig
tuna: no need to disable preloading of EGL drivers

Change-Id: Ia5ac4ee58bc27b3bddd23e1ecb9fcf6a0be46f8d