Kernel: Allow fchmod() and fchown() on pre-bind() local sockets

In order to ensure a specific owner and mode when the local socket
filesystem endpoint is instantiated, we need to be able to call
fchmod() and fchown() on a socket fd between socket() and bind().

This is because until we call bind(), there is no filesystem inode
for the socket yet.

Kernel/FileSystem/File.h

@@ -57,6 +57,8 @@ public:
     virtual String absolute_path(const FileDescription&) const = 0;
 
     virtual KResult truncate(off_t) { return KResult(-EINVAL); }
+    virtual KResult chown(uid_t, gid_t) { return KResult(-EBADF); }
+    virtual KResult chmod(mode_t) { return KResult(-EBADF); }
 
     virtual const char* class_name() const = 0;