ec_commands: Add EC_HOST_EVENT_NONE
ec_commands: Add EC_HOST_EVENT_NONE

ACPI requires event 0 to represent no event. Add EC_HOST_EVENT_NONE=0
to host_event_code to improve readability when there's no event.

BUG=b:184074997
TEST=Build and boot guybrush
BRANCH=None

Signed-off-by: Rob Barnes <3ced0940a2329ce70499686f01d3d60685ec66ed@google.com>
Change-Id: I04690dd98b0e5b8ee9e002279b238c500e364398
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2964955
Reviewed-by: Raul E Rangel <9a9c998e11a2655b1de9a05eeeef5f710c0dc7ed@chromium.org>
Reviewed-by: Furquan Shaikh <6be5c96c464778f89679b1062a2e0a6af93d2aa5@chromium.org>

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