dm: ahci: Avoid scsi_scan_dev() in ahci_probe_scsi()

Running 'scsi scan' command causes scsi_scan_dev() to be called,
from which device_probe() is called and consequently AHCI driver
probe routine will be called as SCSI driver's parent, and finally
ahci_probe_scsi() calls scsi_scan_dev() again.

Remove the call to scsi_scan_dev() in ahci_probe_scsi().

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>