ARM: dts: msm: Disable build of msm8996-v2 CDP boards

Disable build of msm8996-v2 and apq8096-v2 CDP board
variants since they are no longer in active use.
This is being done to free up some static space from
DT blob.

Change-Id: I997759c34891a7289088c852f3b7c18973961741
Signed-off-by: Kaushal Kumar <kaushalk@codeaurora.org>