Add guards for mbedtls_psa_crypto_free()

Signed-off-by: Przemek Stekiel <przemyslaw.stekiel@mobica.com>
diff --git a/programs/fuzz/fuzz_pubkey.c b/programs/fuzz/fuzz_pubkey.c
index 8946973..63c57b6 100644
--- a/programs/fuzz/fuzz_pubkey.c
+++ b/programs/fuzz/fuzz_pubkey.c
@@ -72,9 +72,11 @@
             abort();
         }
     }
+#if defined(MBEDTLS_USE_PSA_CRYPTO)
 exit:
-    mbedtls_pk_free(&pk);
     mbedtls_psa_crypto_free();
+#endif /* MBEDTLS_USE_PSA_CRYPTO */
+mbedtls_pk_free(&pk);
 #else
     (void) Data;
     (void) Size;