bundle_firmware: Add enable-serial to gbb_flag_properties

BUG=chromium:210230
BRANCH=None
TEST=Add gbb-flag-enable-serial to jerry fmap.dts. Verify flag is set on
the emerge-veyron_jerry chromeos-bootimage.

Change-Id: I68e773118bee5a3c74d4c8832e5f1daf1d1a4f76
Signed-off-by: Mary Ruthven <mruthven@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/312830
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/host/lib/bundle_firmware.py b/host/lib/bundle_firmware.py
index 612a7c6..7f10c4d 100644
--- a/host/lib/bundle_firmware.py
+++ b/host/lib/bundle_firmware.py
@@ -71,6 +71,7 @@
   'default-dev-boot-legacy': 0x00000400,
   'disable-pd-software-sync': 0x00000800,
   'force-dev-boot-fastboot-full-cap': 0x00002000,
+  'enable-serial': 0x00004000,
 }
 
 # Maps board name to Exynos product number