vhost: replace -1 with VHOST_FILE_UNBIND in ioctls

This commit replaces -1 with VHOST_FILE_UNBIND in ioctls since
we have added such a macro in the uapi header for vdpa_host.

Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/1591352835-22441-5-git-send-email-lingshan.zhu@intel.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vhost/vhost.c

@@ -1612,7 +1612,7 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg
 			r = -EFAULT;
 			break;
 		}
-		eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
+		eventfp = f.fd == VHOST_FILE_UNBIND ? NULL : eventfd_fget(f.fd);
 		if (IS_ERR(eventfp)) {
 			r = PTR_ERR(eventfp);
 			break;
@@ -1628,7 +1628,7 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg
 			r = -EFAULT;
 			break;
 		}
-		ctx = f.fd == -1 ? NULL : eventfd_ctx_fdget(f.fd);
+		ctx = f.fd == VHOST_FILE_UNBIND ? NULL : eventfd_ctx_fdget(f.fd);
 		if (IS_ERR(ctx)) {
 			r = PTR_ERR(ctx);
 			break;
@@ -1640,7 +1640,7 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg
 			r = -EFAULT;
 			break;
 		}
-		ctx = f.fd == -1 ? NULL : eventfd_ctx_fdget(f.fd);
+		ctx = f.fd == VHOST_FILE_UNBIND ? NULL : eventfd_ctx_fdget(f.fd);
 		if (IS_ERR(ctx)) {
 			r = PTR_ERR(ctx);
 			break;
@@ -1765,7 +1765,7 @@ long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *argp)
 		r = get_user(fd, (int __user *)argp);
 		if (r < 0)
 			break;
-		ctx = fd == -1 ? NULL : eventfd_ctx_fdget(fd);
+		ctx = fd == VHOST_FILE_UNBIND ? NULL : eventfd_ctx_fdget(fd);
 		if (IS_ERR(ctx)) {
 			r = PTR_ERR(ctx);
 			break;