soc: qcom: msm_rtb: Add support for hotplug RTB logging

Hotplug events are particularly interesting from system
point of view and tracing around the hotplug events would
provide essential information that could be used to debug
system issues.

Change-Id: I23e9539a76e04e222a0a05f27be51cb726ab6c33
Signed-off-by: Sanrio Alvares <salvares@codeaurora.org>