dm: scsi: Add a device pointer to scan_exec(), scsi_bus_reset()

dm: scsi: Add a device pointer to scan_exec(), scsi_bus_reset()

With driver model these functions need a device pointer. Add one even
when CONFIG_DM_SCSI is not defined. This avoids having ugly conditional
function prototypes, When CONFIG_DM_SCSI is not defined we can just ignore
the pointer.

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