page cache: Convert find_get_entries_tag to XArray

Slightly shorter and simpler code.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index c9bbb9a..226f96f 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -373,7 +373,7 @@
 					nr_pages, pages);
 }
 unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start,
-			int tag, unsigned int nr_entries,
+			xa_mark_t tag, unsigned int nr_entries,
 			struct page **entries, pgoff_t *indices);
 
 struct page *grab_cache_page_write_begin(struct address_space *mapping,