ARM: dts: msm: remove unsupported entries from mdss for msm8937

Remove unsupported RGB pipe debug entries which are present
in the MDSS DT for msm8937.

Change-Id: I515f3ca9b881e6870af6b99bca7618075a987737
Signed-off-by: Krishna Chaitanya Devarakonda <kdevarak@codeaurora.org>