HW uses host memory as a backing store for a number of
protocol context objects and queue state tracking.
The Host Memory Cache (HMC) is a component responsible for
managing these objects stored in host memory.

Add the functions and data structures to manage the allocation
of backing pages used by the HMC for the various objects

Link: https://lore.kernel.org/r/20210602205138.889-5-shiraz.saleem@intel.comSigned-off-by: Mustafa Ismail <mustafa.ismail@intel.com>
Signed-off-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>