virtio-fs: fix incorrect check for fsvq->kobj

virtio-fs: fix incorrect check for fsvq->kobj

In virtio_fs_add_queues_sysfs(), the code incorrectly checks fs->mqs_kobj
after calling kobject_create_and_add(). Change the check to fsvq->kobj
(fs->mqs_kobj -> fsvq->kobj) to ensure the per-queue kobject is
successfully created.

Fixes: 87cbdc396a31 ("virtio_fs: add sysfs entries for queue information")
Signed-off-by: Alok Tiwari <alok.a.tiwari@oracle.com>
Link: https://patch.msgid.link/20251027104658.1668537-1-alok.a.tiwari@oracle.com
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>