f2fs: simplify __allocate_data_block

[ Upstream commit 3cf684f2 ]

Just use a simple if block for the conditional call to
inc_valid_block_count.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Stable-dep-of: 54607494 ("f2fs: compress: fix to avoid inconsistence bewteen i_blocks and dnode")
Signed-off-by: Sasha Levin <sashal@kernel.org>