Fix signature for MotionEvent#setButtonState

Bug: 31441257

Change-Id: I5069118d6d89f0c3a0eedf85d1d4dafbbec77ac6
diff --git a/include/input/Input.h b/include/input/Input.h
index 55787e7..cfcafab 100644
--- a/include/input/Input.h
+++ b/include/input/Input.h
@@ -398,7 +398,7 @@
 
     inline int32_t getButtonState() const { return mButtonState; }
 
-    inline int32_t setButtonState(int32_t buttonState) { mButtonState = buttonState; }
+    inline void setButtonState(int32_t buttonState) { mButtonState = buttonState; }
 
     inline int32_t getActionButton() const { return mActionButton; }