BACKPORT: f2fs: introduce FI_COMPRESS_RELEASED instead of using IMMUTABLE bit

commit c61404153eb6 upstream.

Once we release compressed blocks, we used to set IMMUTABLE bit. But it turned
out it disallows every fs operations which we don't need for compression.

Let's just prevent writing data only.

Bug: 237904436
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Change-Id: I3f91a67da56fe26e39a776a5bc595aa809dc804b