MINOR: ssl: BoringSSL ocsp_response does not need issuer

HAproxy can fail when issuer is not found, it must not with BoringSSL.
diff --git a/src/ssl_sock.c b/src/ssl_sock.c
index 770216d..aaa8652 100644
--- a/src/ssl_sock.c
+++ b/src/ssl_sock.c
@@ -3281,6 +3281,7 @@
 		}
 	}
 
+#ifndef OPENSSL_IS_BORINGSSL /* Useless for BoringSSL */
 	if (ckch->ocsp_response) {
 		X509 *issuer;
 		int i;
@@ -3321,6 +3322,7 @@
 			}
 		}
 	}
+#endif
 
 	ret = 0;