sched_tp: Add sched_pelt_thermal trace event

...
hackbench-3060 [007] 565.489752: sched_pelt_thermal: cpu=7 load=101 runnable=103765 util=951 update_time=564835470336
hackbench-3147 [005] 565.489760: sched_pelt_thermal: cpu=5 load=101 runnable=104036 util=954 update_time=565325810688
task_n3-3-576  [000] 565.489763: sched_pelt_thermal: cpu=0 load=31 runnable=32404 util=953 update_time=557800611840
hackbench-862  [001] 565.489763: sched_pelt_thermal: cpu=1 load=31 runnable=32395 util=952 update_time=564421108736
hackbench-2136 [002] 565.489763: sched_pelt_thermal: cpu=2 load=31 runnable=32455 util=954 update_time=564142488576

The actual PELT thermal signal is `load`, `runnable` and `util` are
meaningless. It's plotted here since the trace event is implemented
according to the `sched_pelt_rq_template` trace event class.
The `sched_pelt_rt`, `sched_pelt_dl` and `sched_pelt_irq` trace event
have a similar issue.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>