board: gateworks: venice: assume emmc device for USB boot

When booting from USB (SDP) setup firmware-update environment
for emmc device.

Signed-off-by: Tim Harvey <tharvey@gateworks.com>
diff --git a/board/gateworks/venice/venice.c b/board/gateworks/venice/venice.c
index 803582c..3067480 100644
--- a/board/gateworks/venice/venice.c
+++ b/board/gateworks/venice/venice.c
@@ -155,6 +155,7 @@
 		bootdev = 2;
 		break;
 	default:
+		bootdev = 2; /* assume SDHC3 (eMMC) if booting over SDP */
 		break;
 	}
 	if (bootdev != -1)