Allow easily disabling of SPHINCS+.

Author: anhu

wolfssl/wolfcrypt/settings.h

@@ -2978,7 +2978,9 @@ extern void uITRON4_free(void *p) ;
 #define HAVE_PQC
 #define HAVE_FALCON
 #define HAVE_DILITHIUM
-#define HAVE_SPHINCS
+#ifndef WOLFSSL_NO_SPHINCS
+    #define HAVE_SPHINCS
+#endif
 #ifndef WOLFSSL_HAVE_KYBER
     #define WOLFSSL_HAVE_KYBER
     #define WOLFSSL_KYBER512