coresight: etm4x: Fix ETM probe when booting without all cores

We need to fail probe when ETM init fails due to CPU being unavailable
at probe time. There is no current support to defer probe when we hot
plug in the CPU. Also, check for the architecture version of ETM HW
only when ETM init is successful.

Change-Id: I0fc7b3ca5c919a74dfecedcd6278a0e0679f276f
Signed-off-by: Satyajit Desai <sadesai@codeaurora.org>