zephyr: stub system_hibernate
zephyr: stub system_hibernate

Needed by power sequencing.  Doing nothing will work fine for now.

BUG=b:173787365
BRANCH=none
TEST=compile with power sequencing

Signed-off-by: Jack Rosenthal <d3f605bef1867f59845d4ce6e4f83b8dc9e4e0ae@chromium.org>
Change-Id: Ia4e48d92ebbee7a788e4515f6583095349aea0f3
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2548306
Reviewed-by: Jett Rink <9d4aef0593e6843318d99df31597fb6153b89787@chromium.org>

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