hid/controller/npad: Remove #pragma once from the cpp file

This is only useful in headers.

src/core/hle/service/hid/controllers/npad.cpp

@@ -2,8 +2,6 @@
 // Licensed under GPLv2 or any later version
 // Refer to the license.txt file included.
 
-#pragma once
-
 #include <algorithm>
 #include <array>
 #include <cstring>