platform/chrome: cros_ec_proto: drop unneeded BUG_ON() in prepare_packet()

prepare_packet() gets called if `ec_dev->proto_version` > 2.  For now, it
must be equivalent to EC_HOST_REQUEST_VERSION.

Drop the BUG_ON().
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
Link: https://lore.kernel.org/r/20220513044143.1045728-2-tzungbi@kernel.org

drivers/platform/chrome/cros_ec_proto.c

@@ -60,7 +60,6 @@ static int prepare_packet(struct cros_ec_device *ec_dev,
 	int i;
 	u8 csum = 0;
 
-	BUG_ON(ec_dev->proto_version != EC_HOST_REQUEST_VERSION);
 	BUG_ON(msg->outsize + sizeof(*request) > ec_dev->dout_size);
 
 	out = ec_dev->dout;