ARM: dts: msm: Remove the DSU PMU support for sm8150

Remove the DT node that supports the ARM DynamIQ Shared Unit (DSU)
PMU as it is no longer needed by the platform.

Change-Id: I1a4c6cf4046726bc94ee5baf9f68c79cebf0d58e
Signed-off-by: Raghavendra Rao Ananta <rananta@codeaurora.org>