SAE: Store commit scalars as bignum instead of octet string

This avoids unnecessary bignum initialization steps during the SAE
exchange.

Signed-hostap: Jouni Malinen <j@w1.fi>

src/crypto/crypto_openssl.c

@@ -1000,6 +1000,12 @@ int crypto_bignum_bits(const struct crypto_bignum *a)
 }
 
 
+int crypto_bignum_is_zero(const struct crypto_bignum *a)
+{
+	return BN_is_zero((const BIGNUM *) a);
+}
+
+
 #ifdef CONFIG_ECC
 
 struct crypto_ec {