btrfs: get rid of compressed_folios[] usage for compressed read

btrfs: get rid of compressed_folios[] usage for compressed read

Currently btrfs_submit_compressed_read() still uses
compressed_bio::compressed_folios[] array.

Change it to allocate each folio and queue them into the compressed bio
so that we do not need to allocate that array.

Considering how small each compressed read bio is (less than 128KiB), we
do not benefit that much from btrfs_alloc_folio_array() anyway,
while we may benefit more from btrfs_alloc_compr_folio() by using
the global folio pool.

So changing from btrfs_alloc_folio_array() to btrfs_alloc_compr_folio()
in a loop should still be fine.

This removes one error path, and paves the way to completely remove
compressed_folios[] array.

Reviewed-by: Boris Burkov <boris@bur.io>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>