netfs: Remove unnecessary references to pages

These places should all use folios instead of pages.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Link: https://lore.kernel.org/r/20241005182307.3190401-4-willy@infradead.org


Signed-off-by: Christian Brauner <brauner@kernel.org>