[PATCH] libata-hp-prep: implement sata_phy_debounce()

[PATCH] libata-hp-prep: implement sata_phy_debounce()

With hotplug, PHY always needs to be debounced before a reset as any
reset might find new devices.  Extract PHY waiting code from
sata_phy_resume() and extend it to include SStatus debouncing.  Note
that sata_phy_debounce() is superset of what used to be done inside
sata_phy_resume().

Three default debounce timing parameters are defined to be used by
hot/boot plug.  As resume failure during probing will be properly
handled as errors, timeout doesn't have to be long as before.
probeinit() uses the same timeout to retain the original behavior.

Signed-off-by: Tejun Heo <htejun@gmail.com>