mode spec (half of what had been a 32 bit 'driver reserved' value is now
a 16 bit handle that is used to correllate CTIOs with a specific ATIO- we
have to make sure we pass it on thru. Propagate back proper at2_entry
format (instead of one derived from an at_entry). Handles are 16, not
32 bits.
code gratefully borrowed from Patrick Stirling who did a lot of the
grunt work on this years ago. There are also some beginnings of
swizzle macros in case we go to a big endian machine. This is just
a first pass at this and is likely to change a bit over the next
Matt Jacob