Memmap: Replace ValidCopyRange with GetPointerForRange

Source/Core/Core/HW/Memmap.h

@@ -80,7 +80,7 @@ std::string GetString(u32 em_address, size_t size = 0);
 u8* GetPointer(const u32 address);
 void CopyFromEmu(void* data, u32 address, size_t size);
 void CopyToEmu(u32 address, const void* data, size_t size);
-void Memset(const u32 address, const u8 var, const u32 length);
+void Memset(u32 address, u8 value, size_t size);
 u8  Read_U8(const u32 address);
 u16 Read_U16(const u32 address);
 u32 Read_U32(const u32 address);