f2fs: fix to handle filemap_fdatawrite() error in f2fs_ioc_decompress_file/f2fs_ioc_compress_file

It seems inappropriate that the current logic does not handle
filemap_fdatawrite() errors, so let's fix it.

Signed-off-by: Yangtao Li <frank.li@vivo.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>