dwc_ahci: Fix breakage

The dwc_ahci has been broken for quite some time now. The breakage has been
introduced by the series "dm: scsi: Enhance SCSI support for driver model"

Use ahci_bind_scsi() and ahci_probe_scsi() to properly bind and probe the
driver.

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>