lisa.trace: Fix HRTxtTraceParser regex for timestamp parsing

Created by: derkling

A Systrace generated by the Perfetto's traceconv tool has records with this format:

<idle>-0     (-----) [000] .... 608397.919018: sched_wakeup: comm=traced pid=403293 prio=120 target_cpu=000

which timestamp gets parsed as 7.919018, i.e. by ignoring all the digits but one before the second.

Fix the timestamp regexp by ensuring that, after the __cpu filed has been parsed, we skip all and only the non digit chars following it.