x86/mm/pat: Convert split_large_page() to use ptdescs

x86/mm/pat: Convert split_large_page() to use ptdescs

Use the ptdesc APIs for all page table allocation and free sites to
allow their separate allocation from struct page in the future.

Update split_large_page() to allocate a ptdesc instead of allocating a
page for use as a page table.

Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Link: https://patch.msgid.link/20260303194828.1406905-5-vishal.moola@gmail.com