Convert to new probing mechanism and add hotplug support by enabling
PORT_IRQ_PHYRDY_CHG, marking ehi for hotplug and scheduling EH on
PORT_IRQ_PHYRDY_CHG or PORT_IRQ_DEV_XCHG.

Sil3124/32 family of controllers don't have any mechanism to wait for
the first D2H FIS after hotplug, so ATA_FLAG_SKIP_D2H_BSY is used.
Signed-off-by: Tejun Heo <htejun@gmail.com>