kernel: Bump to 3.12.29

kernel: VCHIQ: Add per-service tracing
The new service option VCHIQ_SERVICE_OPTION_TRACE is a boolean that toggles tracing for the specified service.

kernel: vchiq: Make the synchronous-CLOSE logic more tolerant

firmware: deinterlace: Fix for garbage in bottom row of non-32-aligned height
firmware: deinterlace: support half framerate variants
firmware: mmal: allow user flags to be passed through to omx and returned