cros_bundle_firmware: Add option to list available GBB flags

There are quite a few of these - add an option to list them out.

BUG=chromium-os:33312
TEST=manual
$ cros_bundle_firmware -b daisy -v3 --gbb-flags-list
   Available GBB flags:           Hex
   force-dev-boot-legacy          80
   dev-screen-short-delay         01
   force-dev-switch-on            08
   load-option-roms               02
   enable-alternate-os            04
   force-dev-boot-usb             10
   enter-triggers-tonorm          40
   disable-fw-rollback-check      20

Change-Id: Iacb8b9160ea180d60b7dc27e8c766753b48d7bf3
Reviewed-on: https://gerrit.chromium.org/gerrit/36393
Reviewed-by: Randall Spangler <rspangler@chromium.org>
Commit-Ready: Simon Glass <sjg@chromium.org>
Tested-by: Simon Glass <sjg@chromium.org>
diff --git a/host/lib/bundle_firmware.py b/host/lib/bundle_firmware.py
index e5287e6..3cf180d 100644
--- a/host/lib/bundle_firmware.py
+++ b/host/lib/bundle_firmware.py
@@ -69,6 +69,12 @@
   'force-dev-boot-legacy': 0x00000080,
 }
 
+def ListGoogleBinaryBlockFlags():
+  """Print out a list of GBB flags."""
+  print '   %-30s %s' % ('Available GBB flags:', 'Hex')
+  for name, value in gbb_flag_properties.iteritems():
+    print '   %-30s %02x' % (name, value)
+
 class Bundle:
   """This class encapsulates the entire bundle firmware logic.