vhost: Fix ioctl # for VHOST_[GS]ET_FORK_FROM_OWNER

The VHOST_[GS]ET_FEATURES_ARRAY ioctl already took 0x83 and it would
result in a build error when the vhost uapi header is used for perf tool
build like below.

  In file included from trace/beauty/ioctl.c:93:
  tools/perf/trace/beauty/generated/ioctl/vhost_virtio_ioctl_array.c: In function ‘ioctl__scnprintf_vhost_virtio_cmd’:
  tools/perf/trace/beauty/generated/ioctl/vhost_virtio_ioctl_array.c:36:18: error: initialized field overwritten [-Werror=override-init]
     36 |         [0x83] = "SET_FORK_FROM_OWNER",
        |                  ^~~~~~~~~~~~~~~~~~~~~
  tools/perf/trace/beauty/generated/ioctl/vhost_virtio_ioctl_array.c:36:18: note: (near initialization for ‘vhost_virtio_ioctl_cmds[131]’)

Fixes: 7d9896e ("vhost: Reintroduce kthread API and add mode selection")
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Message-Id: <20250819063958.833770-1-namhyung@kernel.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Tested-by: Lei Yang <leiyang@redhat.com>

Author: namhyung

include/uapi/linux/vhost.h

@@ -260,14 +260,14 @@
  * When fork_owner is set to VHOST_FORK_OWNER_KTHREAD:
  *   - Vhost will create vhost workers as kernel threads.
  */
-#define VHOST_SET_FORK_FROM_OWNER _IOW(VHOST_VIRTIO, 0x83, __u8)
+#define VHOST_SET_FORK_FROM_OWNER _IOW(VHOST_VIRTIO, 0x84, __u8)
 
 /**
  * VHOST_GET_FORK_OWNER - Get the current fork_owner flag for the vhost device.
  * Only available when CONFIG_VHOST_ENABLE_FORK_OWNER_CONTROL=y
  *
  * @return: An 8-bit value indicating the current thread mode.
  */
-#define VHOST_GET_FORK_FROM_OWNER _IOR(VHOST_VIRTIO, 0x84, __u8)
+#define VHOST_GET_FORK_FROM_OWNER _IOR(VHOST_VIRTIO, 0x85, __u8)
 
 #endif