ptdesc: convert __page_flags to pt_flags

ptdesc: convert __page_flags to pt_flags

Patch series "Some ptdesc cleanups".

The first two patches here are preparation for splitting struct ptdesc
from struct page and struct folio.  I think their only dependency is on
the memdesc_flags_t patches from August which is in mm-new.  The third
patch is just something I noticed while working on the code.

This patch (of 3):

Use the new memdesc_flags_t type to show that these are the same bits as
page/folio/slab and thesefore have the zone/node/section information in
them.  Remove a use of ptdesc_folio() by converting
pagetable_is_reserved() to use test_bit() directly.

Link: https://lkml.kernel.org/r/20250908171104.2409217-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20250908171104.2409217-2-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>