common/nvdrv: improve memory validation and error handling

Implements several improvements to memory handling and validation:

- host_memory: Add IsValidMapping() and IsDirectMappingEnabled() methods to
  validate memory access
- host_memory: Fix virtual base offset calculation to use proper pointer
  arithmetic
- host_memory: Add size field to track allocation size
- nvhost_ctrl_gpu: Return InvalidState instead of InvalidValue for TPC mask
  buffer size validation
- Update copyright year for citron

The changes improve memory safety by adding explicit validation checks and
fixing pointer arithmetic in the virtual memory implementation.

src/common/host_memory.h

@@ -1,4 +1,5 @@
 // SPDX-FileCopyrightText: Copyright 2019 yuzu Emulator Project
+// SPDX-FileCopyrightText: Copyright 2025 citron Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #pragma once
@@ -82,6 +83,8 @@ private:
 
     // Fallback if fastmem is not supported on this platform
     std::unique_ptr<Common::VirtualBuffer<u8>> fallback_buffer;
+
+    size_t size;
 };
 
 } // namespace Common