tools/power turbostat: fix output buffering issue

In periodic mode, turbostat writes to stdout,
but users were un-able to re-direct stdout, eg.

turbostat > outputfile

would result in an empty outputfile.

Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/tools/power/x86/turbostat/turbostat.c b/tools/power/x86/turbostat/turbostat.c
index 77e76b1..cb03147 100644
--- a/tools/power/x86/turbostat/turbostat.c
+++ b/tools/power/x86/turbostat/turbostat.c
@@ -423,6 +423,7 @@
 void flush_stdout()
 {
 	fputs(output_buffer, stdout);
+	fflush(stdout);
 	outp = output_buffer;
 }
 void flush_stderr()