erofs: get rid of {get,put}_page() for ztailpacking data

The compressed data for the ztailpacking feature is fetched from
the metadata inode (e.g., bd_inode), which is folio-based.

Therefore, the folio interface should be used instead.

Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20250626085459.339830-1-hsiangkao@linux.alibaba.com