msm: perf: tracectr: Initialize cnts after hotplug

Due to the mismatch between counter values saved across CPU hotplug
by perf and tracecounter logic, incorrect values are calculated for
first entry in trace buffer.
Ignore the first entry when CPU comes out of hotplug and set previous
counter values in this scenario.

Change-Id: Ieeeaa301d713f338f11f6e84aeb984a3708e45fc
Signed-off-by: Sheetal Sahasrabudhe <sheetals@codeaurora.org>