drm/i915: Store the default sseu setup on the engine

As we push for better compartmentalisation, it is more convenient to
copy the default sseu configuration from the engine into the derived
logical context, than it is to dig it out from i915->runtime_info.

v2: Use intel_sseu_from_device_info() to describe the converter

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190424095134.30249-1-chris@chris-wilson.co.uk