scsi: bootstage: Measure time taken to scan the bus

On some hardware this time can be significant. Add bootstage support for
measuring this. The result can be obtained using 'bootstage report' or
passed on to the Linux via the device tree.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/common/cmd_scsi.c b/common/cmd_scsi.c
index cbc107e..a0a62eb 100644
--- a/common/cmd_scsi.c
+++ b/common/cmd_scsi.c
@@ -217,8 +217,10 @@
 		       (busdevfunc >> 8) & 0x7);
 	}
 #endif
+	bootstage_start(BOOTSTAGE_ID_ACCUM_SCSI, "ahci");
 	scsi_low_level_init(busdevfunc);
 	scsi_scan(1);
+	bootstage_accum(BOOTSTAGE_ID_ACCUM_SCSI);
 }
 #endif
 
diff --git a/include/bootstage.h b/include/bootstage.h
index df13ab2..6b7588d 100644
--- a/include/bootstage.h
+++ b/include/bootstage.h
@@ -194,6 +194,7 @@
 	BOOTSTAGE_ID_MAIN_CPU_READY,
 
 	BOOTSTAGE_ID_ACCUM_LCD,
+	BOOTSTAGE_ID_ACCUM_SCSI,
 
 	/* a few spare for the user, from here */
 	BOOTSTAGE_ID_USER,