i965/bxt: Add basic Broxton infrastructure

i965/bxt: Add basic Broxton infrastructure

The thread counts and URB information are all speculative numbers that were
based on some CHV numbers at the time.

v2:
Originally this patch had PCI IDs. I've moved that to a new patch at the end of
the series.
Remove is_cherryview hack.
Add PCI ids. These match the ones defined in the kernel. The only one tested by
us is 0x0a84.
Capitalize the hex string (Mark)

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Tested-by: "Lecluse, Philippe" <Philippe.Lecluse@intel.com>
Reviewed-by: Mark Janes <mark.a.janes@intel.com>