tools/power turbostat: on SIGINT: sample, print and exit

When running in interval-mode, catch interrupts
and print a final data record before exiting.

Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/tools/power/x86/turbostat/turbostat.8 b/tools/power/x86/turbostat/turbostat.8
index 04262ab..2dafba4 100644
--- a/tools/power/x86/turbostat/turbostat.8
+++ b/tools/power/x86/turbostat/turbostat.8
@@ -267,6 +267,10 @@
 
 .fi
 
+.SH SIGNALS
+
+SIGINT will interrupt interval-mode.
+The end-of-interval data will be collected and displayed before turbostat exits.
 .SH NOTES
 
 .B "turbostat "