f2fs: Convert dnode_of_data->node_page to node_folio

f2fs: Convert dnode_of_data->node_page to node_folio

All assignments to this struct member are conversions from a folio
so convert it to be a folio and convert all users.  At the same time,
convert data_blkaddr() to take a folio as all callers now have a folio.
Remove eight calls to compound_head().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>