ptr_ring: fix build

Fixes after recent use of kvmalloc
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

tools/virtio/ringtest/ptr_ring.c

@@ -17,6 +17,8 @@
 #define likely(x)    (__builtin_expect(!!(x), 1))
 #define ALIGN(x, a) (((x) + (a) - 1) / (a) * (a))
 #define SIZE_MAX        (~(size_t)0)
+#define KMALLOC_MAX_SIZE SIZE_MAX
+#define BUG_ON(x) assert(x)
 
 typedef pthread_spinlock_t  spinlock_t;
 
@@ -57,6 +59,9 @@ static void kfree(void *p)
 		free(p);
 }
 
+#define kvmalloc_array kmalloc_array
+#define kvfree kfree
+
 static void spin_lock_init(spinlock_t *lock)
 {
 	int r = pthread_spin_init(lock, 0);