ARM: dts: msm: rename coresight etm sysfs node on 9x25

The sysfs ETM node on single core target is currently named coresight-etm,
whereas for multicore targets the nodes appear as coresight-etm0,
coresight-etm1 and so on. Change this to coresight-etm0 on single core
target such as 9x25 to be consistent with multi-core ETM nodes.

Change-Id: Ia2d8c1cc80625a69d86acd6395ea5bbca3ccf5ec
Signed-off-by: Aparna Das <adas@codeaurora.org>