ARM: dts: msm: rename coresight etm sysfs node on 9x35

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 9x35 to be consistent with multi-core ETM nodes.

Change-Id: I4fe79961ef414cb6fa265f5355c9790a8ed7e042
Signed-off-by: Aparna Das <adas@codeaurora.org>