[1] add EN_ENIDMAFIX - the byte-aligner on the ENI version of the card
appears to lose under heavy load so avoid using it. see comment
in midway.c for full details.
note that the Adaptec version of the card works properly under
load.
detected by Kenjiro Cho <kjc@csl.sony.co.jp> [confirmed by chuck]
fix by chuck & kjc
[2] update some freebsd specific code [from kjc]
[3] for circular buffers: ensure there is always one free slot so
that we can easily tell the difference between a full and
empty list. re-structure a few loops to reflect this.
fixes a problem with mbufs being free'd while still in DMA,
and makes drive a bit more robust.
detected and fixed by kjc
d3a7613827