Kernel: Remove UserOrKernelBuffer::copy_into_string()

All former users of this API have been converted to use KString. :^)

Kernel/UserOrKernelBuffer.cpp

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2020, the SerenityOS developers.
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -14,21 +15,6 @@ bool UserOrKernelBuffer::is_kernel_buffer() const
     return !Memory::is_user_address(VirtualAddress(m_buffer));
 }
 
-String UserOrKernelBuffer::copy_into_string(size_t size) const
-{
-    if (!m_buffer)
-        return {};
-    if (Memory::is_user_address(VirtualAddress(m_buffer))) {
-        char* buffer;
-        auto data_copy = StringImpl::create_uninitialized(size, buffer);
-        if (!copy_from_user(buffer, m_buffer, size))
-            return {};
-        return data_copy;
-    }
-
-    return String(ReadonlyBytes { m_buffer, size });
-}
-
 KResultOr<NonnullOwnPtr<KString>> UserOrKernelBuffer::try_copy_into_kstring(size_t size) const
 {
     if (!m_buffer)

Kernel/UserOrKernelBuffer.h

@@ -1,12 +1,12 @@
 /*
  * Copyright (c) 2020, the SerenityOS developers.
+ * Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
 #pragma once
 
-#include <AK/String.h>
 #include <AK/Types.h>
 #include <AK/Userspace.h>
 #include <Kernel/Memory/MemoryManager.h>
@@ -54,7 +54,6 @@ public:
         return offset_buffer;
     }
 
-    [[nodiscard]] String copy_into_string(size_t size) const;
     [[nodiscard]] KResultOr<NonnullOwnPtr<KString>> try_copy_into_kstring(size_t) const;
     [[nodiscard]] bool write(const void* src, size_t offset, size_t len);
     [[nodiscard]] bool write(const void* src, size_t len)