crossystem: support standard --help flag

BUG=chromium:765499
TEST=unittests pass
BRANCH=None

Change-Id: I5c5118c44897d89e5116a9fce49bacbf16704dd8
Reviewed-on: https://chromium-review.googlesource.com/668658
Commit-Ready: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
diff --git a/utility/crossystem.c b/utility/crossystem.c
index 9303b3d..62e8a92 100644
--- a/utility/crossystem.c
+++ b/utility/crossystem.c
@@ -258,7 +258,8 @@
     return PrintAllParams(1);
 
   /* Print help if needed */
-  if (!strcasecmp(argv[1], "-h") || !strcmp(argv[1], "-?")) {
+  if (!strcasecmp(argv[1], "-h") || !strcmp(argv[1], "-?") ||
+      !strcmp(argv[1], "--help")) {
     PrintHelp(progname);
     return 0;
   }