Add PCI device ID for MegaRAID Invader cards.  This was the only
change needed to make it work on my card.

Approved by:	re (glebius)
Re-do r255853.  Along with adding back the API/ABI changes from the
original, this hides the contents of cam_compat.h from ktrace/kdump/truss,
avoiding problems there.  There are no user-servicable parts in there, so
no need for those tools to be groping around in there.

Approved by:	re