tools/power turbostat: Fix child's argument forwarding

Add '+' to optstring when early scanning for --no-msr and --no-perf.
It causes option processing to stop as soon as a nonoption argument is
encountered, effectively skipping child's arguments.

Fixes: 3e404846 ("tools/power turbostat: Add --no-msr option")
Signed-off-by: Patryk Wlazlyn <patryk.wlazlyn@linux.intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>