sata_mv: fix LED blinking for SoC+NCQ

For Marvell SoC chips, the HDD LED does not blink when there is
disk I/O if NCQ is enabled. Add a quirk that enables blink mode for
the LED while NCQ is enabled on any port of a SoC host controller.
Normal LED function is restored when NCQ is not enabled on any port.

The code to enable the blink mode is based on earlier code
and suggestions from Frans Pop, Saeed Bishara, and possibly others.

Signed-off-by: Mark Lord <mlord@pobox.com>
Tested-by: Frans Pop <elendil@planet.nl>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>