ARM: dts: msm: add audio codec as child of MSM External display

Add the audio codec as a child node of the MSM External display
node. The audio codec probe will happen after the External
display probe, and will allow the audio codec to register with
the External display independently of the display interface(s)
that will the added after a hotplug event.

Change-Id: I481e475ceff2ea0a07a0dfc4083526982674954c
CRs-Fixed: 1009284
Signed-off-by: Tatenda Chipeperekwa <tatendac@codeaurora.org>