smbd: remove fsp->dirfsp

smbd: remove fsp->dirfsp

This was supposed to be a shortcut to avoid passing dirfsp around as an explicit
function argument throughout the whole codebase when the new VFS design idea was
based on using *AT functions throughout the VFS.

Now that we've opted for basing the VFS on handles and *AT functions will only
be used in a much more limitted extent, it makes sense to remove this internal
dirfsp reference, otherwise the combination of internal fsp->dirfsp and
smb_fname->fsp is going to be a tough to wrap your head around.

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>