gfs2: support ludicrously large folios in gfs2_trans_add_databufs()

We may someday support folios larger than 4GB, so use a size_t for the
byte count within a folio to prevent unpleasant truncations.

Link: https://lkml.kernel.org/r/20230612210141.730128-6-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Tested-by: Bob Peterson <rpeterso@redhat.com>
Reviewed-by: Bob Peterson <rpeterso@redhat.com>
Reviewed-by: Andreas Gruenbacher <agruenba@redhat.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>