IB/ipath: User mode send DMA header file

A new header file which allows the IBA7220 send DMA engine to be used
from userland.  The definitions here are not used yet, that will happen
in a follow-on patch...

Signed-off-by: Arthur Jones <arthur.jones@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>