parent_dmat DMA tag leaked on all error paths (never destroyed)

Summary

bt_pci_attach creates bt->parent_dmat via bus_dma_tag_create but neither bt_pci_release_resources nor bt_free_softc ever calls bus_dma_tag_destroy on it. Every error path in bt_pci_attach that calls bt_pci_release_resources leaks the tag permanently. No device_detach method registered so even on normal device removal tag never freed. All five comparable SCSI HBA PCI drivers in same tree explicitly destroy parent_dmat (mpt_pci.c:772 adv_pci.c:212/222 advansys.c:769 adwcam.c:880). Resource leak not memory-safety defect. Trigger: hardware presenting BusLogic PCI device that fails bt_probe or privileged user forcing re-probe.