platform/chrome: cros_ec_proto: Upgrade get_next_event to v3

Upgrade EC_CMD_GET_NEXT_EVENT to version 3.

The max supported version will be v3. So, we speak v3 even if the EC
says it supports v4+.

Signed-off-by: Daisuke Nojiri <dnojiri@chromium.org>
Link: https://lore.kernel.org/r/20240604230837.2878737-1-dnojiri@chromium.org


[tzungbi: uint32_t -> u32 per suggested by checkpatch.pl]
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>