platform/chrome: cros_ec_lpc: Add MKBP events support over ACPI

This patch installs a notify handler to process MKBP events for EC
firmware directing them over ACPI.

Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
Signed-off-by: Benson Leung <bleung@chromium.org>