trace: Relax trace-events parsing regex in simpletrace.py

trace: Relax trace-events parsing regex in simpletrace.py

The regular expression to parse trace event definitions assumed the
format string would be a simple double-quoted string.  However, we now
use PRI?64 for portability which splits string literals.  The regular
expression can disregard the format string entirely since simpletrace.py
never needs to use it.

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>