erofs: remove unnecessary output in erofs_show_options()

We have already handled cache_strategy option carefully,
so incorrect setting could not pass option parsing.
Meanwhile, print 'cache_strategy=(unknown)' can cause
failure on remount.

Link: https://lore.kernel.org/r/20191119115049.3401-1-cgxu519@mykernel.netSigned-off-by: NChengguang Xu <cgxu519@mykernel.net>
Reviewed-by: NGao Xiang <gaoxiang25@huawei.com>
Reviewed-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NGao Xiang <gaoxiang25@huawei.com>

fs/erofs/super.c

@@ -598,9 +598,6 @@ static int erofs_show_options(struct seq_file *seq, struct dentry *root)
 		seq_puts(seq, ",cache_strategy=readahead");
 	} else if (sbi->cache_strategy == EROFS_ZIP_CACHE_READAROUND) {
 		seq_puts(seq, ",cache_strategy=readaround");
-	} else {
-		seq_puts(seq, ",cache_strategy=(unknown)");
-		DBG_BUGON(1);
 	}
 #endif
 	return 0;