Add support for SATA part of Marvell 88SE912x controllers to ahci(4). Limit early revisions from 6Gb/s to 3Gb/s by default, or they negotiate only 1.5Gb/s, when 3Gb/s devices connected. Add dummy driver for PATA part of these controllers, preventing generic driver attach them. It causes system freeze when SATA controller used after PATA was touched.