ioatdma: disable RAID on non-Atom platforms and reenable unaligned copies

Disable RAID on non-Atom platform and remove related fixups such as the
64-byte alignement restriction on legacy DMA operations (introduced in
commit f26df1a1 as a workaround for silicon errata).

Signed-off-by: Brice Goglin <Brice.Goglin@inria.fr>
Acked-by: Dave Jiang <dave.jiang@intel.com>
Acked-by: Jon Mason <jon.mason@intel.com>
Signed-off-by: Dan Williams <djbw@fb.com>