tools/power turbostat: Restore GFX sysfs fflush() call

Do fflush() to discard the buffered data, before each read of the
graphics sysfs knobs.

Fixes: ba99a4f ("tools/power turbostat: Remove unnecessary fflush() call")
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

Author: zhang-rui

tools/power/x86/turbostat/turbostat.c

@@ -6039,6 +6039,7 @@ int snapshot_graphics(int idx)
 	int retval;
 
 	rewind(gfx_info[idx].fp);
+	fflush(gfx_info[idx].fp);
 
 	switch (idx) {
 	case GFX_rc6: