ARM: dts: msm: add documentation for msm pmu
ARM: dts: msm: add documentation for msm pmu

Adds device tree documentation for the performance
monitor unit on msm devices.

Change-Id: Id142aaf85fde72c4a347056af7f68da318f00691
Signed-off-by: Neil Leeder <1c3a980dc8904497e49ebc91fe67bb60e7f048ac@codeaurora.org>

TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas