Kernel: Move all code into the Kernel namespace

Kernel/FileSystem/DiskBackedFileSystem.cpp

@@ -32,6 +32,8 @@
 
 //#define DBFS_DEBUG
 
+namespace Kernel {
+
 struct CacheEntry {
     time_t timestamp { 0 };
     u32 block_index { 0 };
@@ -240,3 +242,5 @@ DiskCache& DiskBackedFS::cache() const
         m_cache = make<DiskCache>(const_cast<DiskBackedFS&>(*this));
     return *m_cache;
 }
+
+}