Define IEEE1394_MAX_ASYNC(), which gives the maximum (link speed dependent) asynchronous packet size.
Define IEEE1394_MAX_ASYNC(), which gives the maximum (link speed dependent)
asynchronous packet size.

Idea from NetBSD.

orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars