Fix cppcheck warnings

Signed-off-by: George Liu <liuxiwei@inspur.com>
Change-Id: I18be21d5141630a1da3d5e54740b54a9a06496d9
diff --git a/src/power_button.cpp b/src/power_button.cpp
index 2446d7b..b6a89b9 100644
--- a/src/power_button.cpp
+++ b/src/power_button.cpp
@@ -39,7 +39,8 @@
     return pressedTime;
 }
 
-void PowerButton::handleEvent(sd_event_source* es, int fd, uint32_t revents)
+void PowerButton::handleEvent(sd_event_source* /* es */, int fd,
+                              uint32_t /* revents */)
 {
     int n = -1;
     char buf = '0';