hw/ide: Emulate SiI3112 SATA controller

This is a common generic PCI SATA controller that is also used in PCs
but more importantly guests running on the Sam460ex board prefer this
card and have a driver for it (unlike for other SATA controllers
already emulated).

Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
Acked-by: John Snow <jsnow@redhat.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>