dm: sandbox: Enable SCSI

Enable building the SCSI code for sandbox. This increases build coverage
for sandbox.

Signed-off-by: Simon Glass <sjg@chromium.org>

include/configs/sandbox.h

@@ -202,4 +202,10 @@
 #define CONFIG_SYS_ATA_ALT_OFFSET	2
 #define CONFIG_SYS_ATA_STRIDE		4
 
+#define CONFIG_SCSI
+#define CONFIG_SCSI_AHCI_PLAT
+#define CONFIG_SYS_SCSI_MAX_DEVICE	2
+#define CONFIG_SYS_SCSI_MAX_SCSI_ID	8
+#define CONFIG_SYS_SCSI_MAX_LUN		4
+
 #endif