MSI-X: first cut

The pieces here may be right, but I doubt they are completely right.
Please look hard at the addrhi, vector, and data variables.
Also, not sure I'm allocating enough contig pages.
There can be up to 2^10 entries, each entry is 16 bytes. That's
2^14 bytes I think?

Signed-off-by: Ronald G. Minnich <rminnich@google.com>