Kernel: Add accessor for mount host custody

There's no reason this information needs to be secret.

Kernel/FileSystem/Mount.cpp

@@ -48,4 +48,14 @@ RefPtr<Inode const> Mount::host() const
     return m_host_custody->inode();
 }
 
+RefPtr<Custody const> Mount::host_custody() const
+{
+    return m_host_custody;
+}
+
+RefPtr<Custody> Mount::host_custody()
+{
+    return m_host_custody;
+}
+
 }

Kernel/FileSystem/Mount.h

@@ -28,6 +28,9 @@ public:
     RefPtr<Inode const> host() const;
     RefPtr<Inode> host();
 
+    RefPtr<Custody const> host_custody() const;
+    RefPtr<Custody> host_custody();
+
     Inode const& guest() const { return *m_guest; }
     Inode& guest() { return *m_guest; }