dt-bindings: display/msm: qcom,mdp5: drop lut clock

None of MDP5 platforms have a LUT clock on the display-controller, it
was added by the mistake. Drop it, fixing DT warnings on MSM8976 /
MSM8956 platforms. Technically it's an ABI break, but no other platforms
are affected.

Fixes: 385c8ac7 ("dt-bindings: display/msm: convert MDP5 schema to YAML format")
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Patchwork: https://patchwork.freedesktop.org/patch/667822/


Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>