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>