drm/i915: Add EU stride runtime parameter

drm/i915: Add EU stride runtime parameter

Add a new SSEU runtime parameter, eu_stride, which is
used to mirror the userspace concept of a range of EUs
per subslice.

This patch simply adds the parameter and updates usage
in the QUERY_TOPOLOGY_INFO handler.

v2: Add GEM_BUG_ON to make sure eu_stride is valid

Signed-off-by: Stuart Summers <stuart.summers@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190823160307.180813-5-stuart.summers@intel.com