gfs2: convert stuffed_readpage() to stuffed_read_folio()

Use folio_fill_tail() to implement the unstuffing and folio_end_read() to
simultaneously mark the folio uptodate and unlock it.  Unifies a couple of
code paths.

Link: https://lkml.kernel.org/r/20231107212643.3490372-4-willy@infradead.org


Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Andreas Gruenbacher <agruenba@redhat.com>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Darrick J. Wong <djwong@kernel.org>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>