nucleo-f412zg: Enable blink example
nucleo-f412zg: Enable blink example

This mirrors what we already do with the other nucleo-h743zi
test platform.
github.com/coreboot/chrome-ec/blob/HEAD/board/nucleo-h743zi/board.h#L31

BRANCH=none
BUG=none
TEST=make BOARD=nucleo-f412zg
     # Flash to nucleo
     # Check lights are counting in binary

Change-Id: I3bb708e54e9d7cc0c8ccd9b36e12843d3ca547bf
Signed-off-by: Craig Hesling <383db090fd8ef907a606ac8a9eccd2962bc489cf@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2587571
Reviewed-by: Scott Collyer <7d40b3eb9e17bf55d972074a5e77a7ea4159f9dd@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec