Add a default implementation for VOP_VPTOCNP(9) which scans the parent directory of a vnode to find a dirent with a matching file number.  The name from that dirent is then used to provide the component name.
Add a default implementation for VOP_VPTOCNP(9) which scans the parent
directory of a vnode to find a dirent with a matching file number.  The
name from that dirent is then used to provide the component name.

Note: if the initial vnode argument is not a directory itself, then
the default VOP_VPTOCNP(9) implementation still returns ENOENT.

Reviewed by:	kib
Approved by:	kib
Tested by:	pho

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