ATA: pata_octeon_cf: Use I/O clock rate for timing calculations.

The creation of the I/O clock domain requires some adjustments.  Since the
CF bus timing logic is clocked by the I/O clock, use its rate for delay
calculations.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Cc: Jeff Garzik <jgarzik@pobox.com>
Cc: linux-ide@vger.kernel.org
Patchwork: http://patchwork.linux-mips.org/patch/1660/
Acked-by: Jeff Garzik <jgarzik@redhat.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>