Hibmc use the devm_drm_dev_alloc function in hibmc_pci_probe, if
hibmc_pci_probe returns non-zero, devm_drm_dev_alloc will call
devm_drm_dev_init, which will call devm_drm_dev_init_release to
release drm_dev_put. There is no need for hibmc to call
drm_dev_put separately.