Address security concerns for vboot_audio.c

Based on the compile-time constants, I don't think we were in any danger,
but I've added the checks anyway. It never hurts to be certain!

BUG=chromium-os:22786
TEST=none

Change-Id: I469dda19b4589e484a41ca9bae1e107787f3cf4d
Reviewed-on: https://gerrit.chromium.org/gerrit/11516
Tested-by: Bill Richardson <wfrichar@chromium.org>
Reviewed-by: Gaurav Shah <gauravsh@chromium.org>
1 file changed