WIP: samsung-hero2lte: kernel update (3.18.140), use packaged exynos-dtbtool and enable wifi support

Self-explanatory, really.

The former of the two changes will have to be repeated to hero but I don't have an S7 flat to test, it should be fairly easy to port over (it's what I did for wifi support.)

Also went ahead and updated the downstream kernel since it was available.