ntfs3: stop using write_cache_pages

ntfs3: stop using write_cache_pages

Patch series "remove write_cache_pages()".

Kill off write_cache_pages() after converting the last two users to the
iterator.

This patch (of 3):

Stop using the obsolete write_cache_pages and use writeback_iter directly.

Link: https://lkml.kernel.org/r/20250818061017.1526853-1-hch@lst.de
Link: https://lkml.kernel.org/r/20250818061017.1526853-2-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>