BACKPORT: f2fs: compress: fix to update i_compr_blocks correctly

Previously, we account reserved blocks and compressed blocks into
@compr_blocks, then, f2fs_i_compr_blocks_update(,compr_blocks) will
update i_compr_blocks incorrectly, fix it.

Meanwhile, for the case all blocks in cluster were reserved, fix to
update dn->ofs_in_node correctly.

Bug: 378001005
Fixes: eb8fbaa5 ("f2fs: compress: fix to check unreleased compressed cluster")
Change-Id: Ie195fc57a1d55ff9f42fe4855edd21da1c88bb90
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
(cherry picked from commit 186e7d71)