zephyr: add zephyr/include to include path
zephyr: add zephyr/include to include path

This directory was brought over from zephyr-chrome.

BUG=b:2633887
BRANCH=none
TEST=zmake testall

Signed-off-by: Jack Rosenthal <d3f605bef1867f59845d4ce6e4f83b8dc9e4e0ae@chromium.org>
Change-Id: Ib0d77cc7eb1c6e2fb35a2d7f529b6100d7bd5bb3
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2633648
Commit-Queue: Simon Glass <c00b0378376498bd9cd974c388df8854c0131d27@chromium.org>
Reviewed-by: Simon Glass <c00b0378376498bd9cd974c388df8854c0131d27@chromium.org>

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