libspdm_hmac_new returns incorrect type

[steven-bellock]

libspdm/library/spdm_crypt_lib/libspdm_crypt_hmac.c

Lines 9 to 18 in 87d6c6c

	void *libspdm_hmac_new(uint32_t base_hash_algo)
	{
	switch (base_hash_algo) {
	case SPDM_ALGORITHMS_BASE_HASH_ALGO_TPM_ALG_SHA_256:
	#if LIBSPDM_SHA256_SUPPORT
	return libspdm_hmac_sha256_new();
	#else
	LIBSPDM_ASSERT(false);
	return false;
	#endif

Function return type is void * but some paths return false instead of NULL.