Btrfs: Cocci spatch "memdup.spatch"

diff -u -p a/fs/btrfs/send.c b/fs/btrfs/send.c
@@ -3429,10 +3429,9 @@ static int __find_xattr(int num, struct
 	    strncmp(name, ctx->name, name_len) == 0) {
 		ctx->found_idx = num;
 		ctx->found_data_len = data_len;
-		ctx->found_data = kmalloc(data_len, GFP_NOFS);
+		ctx->found_data = kmemdup(data, data_len, GFP_NOFS);
 		if (!ctx->found_data)
 			return -ENOMEM;
-		memcpy(ctx->found_data, data, data_len);
 		return 1;
 	}
 	return 0;