al_eth: Use the common RSS key

Fetch the common Toeplitz key instead of filling it with random bytes
during receive-forwarding setup.  Check the key size at compile time and
retain the existing host-to-network conversion for each hardware word.

Leave forwarding, hash selection, and queue mapping unchanged.

Reviewed by:	gallatin
MFC after:	2 weeks
Sponsored by:	BBOX.io
Differential Revision:	https://reviews.freebsd.org/D59804

sys/dev/al_eth/al_eth.c

@@ -55,6 +55,7 @@
 #include <net/if_types.h>
 #include <netinet/in.h>
 #include <net/if_vlan_var.h>
+#include <net/rss_config.h>
 #include <netinet/tcp.h>
 #include <netinet/tcp_lro.h>
 
@@ -2960,8 +2961,9 @@ al_eth_config_rx_fwd(struct al_eth_adapter *adapter)
 	al_eth_mac_table_promiscuous_set(adapter, false);
 
 	/* set toeplitz hash keys */
-	for (i = 0; i < sizeof(adapter->toeplitz_hash_key); i++)
-		*((uint8_t*)adapter->toeplitz_hash_key + i) = (uint8_t)random();
+	_Static_assert(sizeof(adapter->toeplitz_hash_key) == RSS_KEYSIZE,
+	    "RSS key size mismatch");
+	rss_getkey((uint8_t *)adapter->toeplitz_hash_key);
 
 	for (i = 0; i < AL_ETH_RX_HASH_KEY_NUM; i++)
 		al_eth_hash_key_set(&adapter->hal_adapter, i,