Allow cxgbe(4) to be built on i386. Driver attach will succeed only on a subset

of i386 systems.

sys/dev/cxgbe/t4_main.c

@@ -668,6 +668,14 @@ t4_attach(device_t dev)
 		goto done;
 	}
 
+#if defined(__i386__)
+	if ((cpu_feature & CPUID_CX8) == 0) {
+		device_printf(dev, "64 bit atomics not available.\n");
+		rc = ENOTSUP;
+		goto done;
+	}
+#endif
+
 	/* Prepare the firmware for operation */
 	rc = prep_firmware(sc);
 	if (rc != 0)

sys/dev/cxgbe/t4_mp_ring.c

@@ -38,6 +38,11 @@ __FBSDID("$FreeBSD$");
 
 #include "t4_mp_ring.h"
 
+#if defined(__i386__)
+#define atomic_cmpset_acq_64 atomic_cmpset_64
+#define atomic_cmpset_rel_64 atomic_cmpset_64
+#endif
+
 union ring_state {
 	struct {
 		uint16_t pidx_head;