vfs_not_implemented: do not mark structs with _PUBLIC_

vfs_not_implemented: do not mark structs with _PUBLIC_

Commit 5d295e41af4e9316aee1b4cf1c3087663b7c06a4 accidentally marked
some structs with _PUBLIC_, which causes clang to complain:

../../source3/modules/vfs_not_implemented.c:594:1: error: attribute 'visibility' is ignored, place it after "struct" to apply attribute to type declaration [-Werror,-Wignored-attributes]
_PUBLIC_
^
../../lib/replace/replace.h:917:33: note: expanded from macro '_PUBLIC_'
                                ^
../../source3/modules/vfs_not_implemented.c:642:1: error: attribute 'visibility' is ignored, place it after "struct" to apply attribute to type declaration [-Werror,-Wignored-attributes]
_PUBLIC_
^
../../lib/replace/replace.h:917:33: note: expanded from macro '_PUBLIC_'
                                ^

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Volker Lendecke <vl@samba.org>