vboot_reference: Fix keyboard input lag at confirm screen.

Changing languages is terribly slow at the confirm screen, when
switching from dev to normal. Reduce sleep time to improve user

TEST=boot in dev, hit space, hit arrows rapidly to change language,
observe no lag.
BRANCH=butterfly, stout

Change-Id: I0943debc31d78dcfce87e7f7d4537ae47f5f8cfd
Reviewed-on: https://gerrit.chromium.org/gerrit/36956
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-by: Bill Richardson <wfrichar@chromium.org>
Commit-Ready: Shawn Nematbakhsh <shawnn@google.com>
Tested-by: Shawn Nematbakhsh <shawnn@google.com>
Reviewed-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/37938
Tested-by: Simon Glass <sjg@chromium.org>
diff --git a/firmware/lib/vboot_api_kernel.c b/firmware/lib/vboot_api_kernel.c
index a35fd31..ffcb75c 100644
--- a/firmware/lib/vboot_api_kernel.c
+++ b/firmware/lib/vboot_api_kernel.c
@@ -105,6 +105,8 @@
   return retval;
+#define CONFIRM_KEY_DELAY 20  /* Check confirm screen keys every 20ms */
 /* Ask the user to confirm something. We should display whatever the question
  * is first, then call this. ESC is always "no", ENTER is always "yes", and
  * we'll specify what SPACE means. We don't return until one of those keys is
@@ -139,7 +141,7 @@
       VbCheckDisplayKey(cparams, key, &vnc);
-    VbExSleepMs(1000);
   /* not reached, but compiler will complain without it */
   return -1;