zephyr: shim: add a board_led.h utilities header
zephyr: shim: add a board_led.h utilities header

Add a board_led.h header with a holding structure for custom board LEDs.

BRANCH=none
BUG=b:217741090
TEST=nothing... not used yet

Signed-off-by: Fabio Baltieri <1c55e39c05d9ab42261288cf330256b2af6ba179@google.com>
Change-Id: I52dc4053c79a66366f7b7f937c12a75baf458b27
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3569764
Reviewed-by: Parth Malkan <c3d09dcbffc3a0a63125afed46f55e5cbf5bb3a9@google.com>

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