netboot: Capture failure exceeding the number of retries in u-boot

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
diff --git a/amboar/obmc-scripts/netboot/netboot b/amboar/obmc-scripts/netboot/netboot
index 85c9ecb..8032ea5 100755
--- a/amboar/obmc-scripts/netboot/netboot
+++ b/amboar/obmc-scripts/netboot/netboot
@@ -87,6 +87,7 @@
                     r"## Warning:",
                     r"[*]{3} ERROR:",
                     "Abort",
+                    "Retry count exceeded; starting again",
                 ])
                 if i > 0:
                     print("Error detected, exiting", file=sys.stderr)