soc: qcom: core_hang: Separate sysfs entry for silver and gold cluster

Silver and gold cluster use different PMU_EVENT and may need to have
different threshold values.

This patch creates different sysfs entries for silver and gold cluster.

CRs-Fixed: 1004392
Change-Id: I88cdf5110cadb44a81c0c700d5188bf639bb2129
Signed-off-by: Runmin Wang <runminw@codeaurora.org>