Kernel: Add Device base class for CharacterDevice.

..to prepare for adding a BlockDevice class.

Kernel/CharacterDevice.cpp

@@ -1,20 +1,7 @@
-#include "CharacterDevice.h"
-#include <LibC/errno_numbers.h>
+#pragma once
+
+#include <Kernel/CharacterDevice.h>
 
 CharacterDevice::~CharacterDevice()
 {
 }
-
-RetainPtr<FileDescriptor> CharacterDevice::open(int& error, int options)
-{
-    return VFS::the().open(*this, error, options);
-}
-
-void CharacterDevice::close()
-{
-}
-
-int CharacterDevice::ioctl(Process&, unsigned, unsigned)
-{
-    return -ENOTTY;
-}