intel/aub_write: factorize context image/pphwsp/ring creation

intel/aub_write: factorize context image/pphwsp/ring creation

We allocate GGTT entries and physical addresses are we create engines
rather than having a fixed layout.

Context images now receive a parameter argument which is used to setup
pml4 & ring buffer addresses.

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Rafael Antognolli <rafael.antognolli@intel.com>