netfs: Remove call to folio_index()

Calling folio_index() is pointless overhead; directly dereferencing
folio->index is fine.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Link: https://lore.kernel.org/r/20241005182307.3190401-2-willy@infradead.org
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: Matthew Wilcox (Oracle)

include/trace/events/netfs.h

@@ -451,7 +451,7 @@ TRACE_EVENT(netfs_folio,
 		    struct address_space *__m = READ_ONCE(folio->mapping);
 		    __entry->ino = __m ? __m->host->i_ino : 0;
 		    __entry->why = why;
-		    __entry->index = folio_index(folio);
+		    __entry->index = folio->index;
 		    __entry->nr = folio_nr_pages(folio);
 			   ),