tools/virtio: remove smp_read_barrier_depends()

This gets rid of the last references to smp_read_barrier_depends()
which for the kernel side was removed in v5.9. The serialization
required for Alpha is done inside READ_ONCE() instead of having
users deal with it. Simply use a full barrier, the architecture
does not have rmb in the first place.

Signed-off-by: Davidlohr Bueso <[e-mail]>
Message-Id: <[e-mail]>
Signed-off-by: Michael S. Tsirkin <[e-mail]>
Reviewed-by: Xuan Zhuo <[e-mail]>

tools/virtio/ringtest/main.h

···
 #define smp_wmb() smp_release()
 #endif
 
-#ifdef __alpha__
-#define smp_read_barrier_depends() smp_acquire()
-#else
-#define smp_read_barrier_depends() do {} while(0)
-#endif
-
 static __always_inline
 void __read_once_size(const volatile void *p, void *res, int size)
 {
···
 	}
 }
 
+#ifdef __alpha__
 #define READ_ONCE(x) \
 ({									\
 	union { typeof(x) __val; char __c[1]; } __u;			\
 	__read_once_size(&(x), __u.__c, sizeof(x));		\
-	smp_read_barrier_depends(); /* Enforce dependency ordering from x */ \
+	smp_mb(); /* Enforce dependency ordering from x */		\
 	__u.__val;							\
 })
+#else
+#define READ_ONCE(x)							\
+({									\
+	union { typeof(x) __val; char __c[1]; } __u;			\
+	__read_once_size(&(x), __u.__c, sizeof(x));			\
+	__u.__val;							\
+})
+#endif
 
 #define WRITE_ONCE(x, val) \
 ({							\