ecryptfs: Convert ecryptfs_read_lower_page_segment() to take a folio

All callers have a folio, so pass it in and use it directly.  This will
not work for large folios, but I doubt anybody wants to use large folios
with ecryptfs.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Link: https://lore.kernel.org/r/20241025190822.1319162-5-willy@infradead.org


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