vhost: (cosmetic) remove a superfluous variable initialisation

Even the compiler is able to figure out that in this case the
initialisation is superfluous.
Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
Link: https://lore.kernel.org/r/20200527180541.5570-3-guennadi.liakhovetski@linux.intel.comSigned-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vhost/vhost.c

@@ -920,7 +920,7 @@ static inline void __user *__vhost_get_user(struct vhost_virtqueue *vq,
 
 #define vhost_put_user(vq, x, ptr)		\
 ({ \
-	int ret = -EFAULT; \
+	int ret; \
 	if (!vq->iotlb) { \
 		ret = __put_user(x, ptr); \
 	} else { \