statinfo.h: move DTYPE defines from dir.h

statinfo.h: move DTYPE defines from dir.h

592fc5b3 (dir.h: move DTYPE defines from cache.h, 2023-04-22) moved
DTYPE macros from cache.h to dir.h, but they are still used by cache.h
to implement ce_to_dtype(); cache.h cannot include dir.h because that
would cause name-hash.c to have two different and conflicting
definitions of `struct dir_entry`. (That should be separately fixed.)

Both dir.h and cache.h include statinfo.h, and this seems a reasonable
place for these definitions.

This change fixes a broken build issue on old SunOS.

Signed-off-by: Alejandro R. Sedeño <asedeno@mit.edu>
Signed-off-by: Alejandro R Sedeño <asedeno@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>