hisi_acc_vfio_pci: Fix reference leak in hisi_acc_vfio_debug_init

hisi_acc_vfio_pci: Fix reference leak in hisi_acc_vfio_debug_init

The debugfs_lookup() function returns a dentry with an increased reference
count that must be released by calling dput().

Fixes: b398f91779b8 ("hisi_acc_vfio_pci: register debugfs for hisilicon migration driver")
Cc: stable@vger.kernel.org
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Reviewed-by: Longfang Liu <liulongfang@huawei.com>
Link: https://lore.kernel.org/r/20250901081809.2286649-1-linmq006@gmail.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>