libata: New driver for OCTEON SOC Compact Flash interface (v7).

Cavium OCTEON processor support was recently merged, so now we have
this CF driver for your consideration.

Most OCTEON variants have *no* DMA or interrupt support on the CF
interface so for these, only PIO is supported.  Although if DMA is
available, we do take advantage of it.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>