lindebugfs_init() creates the "kcov" symlink with debugfs_create_symlink(),
which allocates a node and a copy of the destination, but passed no destroy
callback to pfs_create_link(). pseudofs therefore never released them and
the "debugfsint" malloc type was reported as leaking memory each time the
module was unloaded.

Use debugfs_destroy(), as done for the other nodes.