pata_cs5536: ATA driver for Geode companion chip

This is a driver for the ATA controller on the Geode CS5536 companion
chip.  The PCI device ID for this device was previously claimed by
pata_amd.c but the PIO timings were not correct.  This driver also
works around a bug in some BIOSes that handle unaligned access to the
PCI config registers poorly.  Finally, the driver allows fallback to
using MSR registers for configuration on BIOSes that are truly
broken.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>