reston: Add proper init for boot & cold_reset.

BUG=none
TEST=manual,

sudo emerge hdctools
launch servod with ft230x and vid:pid == 18d1:5007 and use it to
program zinger or other stm32fxxx like devices w/ boot0 and cold_reset
pinned out to CB0 & CB1

Change-Id: Id26eca174b05ba8eb38f8509446116fb0071e1b1
Reviewed-on: https://chromium-review.googlesource.com/226691
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>
Commit-Queue: Todd Broch <tbroch@chromium.org>
Tested-by: Todd Broch <tbroch@chromium.org>
1 file changed