image_signing: output pubkey in DER format

BRANCH=None
BUG=chromium:718184
TEST=new imageloader works

Change-Id: I430ed616954c820d3d1607eefd4f8e1c60863a8f
Reviewed-on: https://chromium-review.googlesource.com/497914
Commit-Ready: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Greg Kerr <kerrnel@chromium.org>
1 file changed