coresight: perf: Allow tracing on hotplugged CPUs

At the moment, if there is no CPU specified for a given
event, we use cpu_online_mask and try to build path for
each of the CPUs in the mask. This could prevent any CPU
that is turned online later to be used for the tracing.

This patch changes to use the cpu_present_mask and tries
to build path for as much CPUs as possible ignoring the
failures in building path for some of the CPUs. If ever
we try to trace on those CPUs, we fail the operation.

Based on a patch from Mathieu Poirier.

Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>