const correctness fixes for OpenSSL 4

Index: tls_verify.c
--- tls_verify.c.orig
+++ tls_verify.c
@@ -213,11 +213,11 @@ tls_check_common_name(struct tls *ctx, X509 *cert, con
     int *cn_match)
 {
 	unsigned char *utf8_bytes = NULL;
-	X509_NAME *subject_name;
+	const X509_NAME *subject_name;
 	char *common_name = NULL;
 	union tls_addr addrbuf;
 	int common_name_len;
-	ASN1_STRING *data;
+	const ASN1_STRING *data;
 	int lastpos = -1;
 	int rv = -1;
 
