ARM: dts: msm: Remove the virtual plane implementation on msm8996

Virtual plane limited the usage of plane on assigned display only.
It is against the implementation in strategy manager in SDM, which
assume any plane can be used by any display.

Change-Id: Iddcb94d888dfa1ec7685f2964116b4296a0e9a7f
Signed-off-by: Camus Wong <camusw@codeaurora.org>
Signed-off-by: Rahul Sharma <sharah@codeaurora.org>