drm/i915: Expand subslice mask

Currently, the subslice_mask runtime parameter is stored as an
array of subslices per slice. Expand the subslice mask array to
better match what is presented to userspace through the
I915_QUERY_TOPOLOGY_INFO ioctl. The index into this array is
then calculated:
  slice * subslice stride + subslice index / 8

v2: fix spacing in set_sseu_info args
    use set_sseu_info to initialize sseu data when building
    device status in debugfs
    rename variables in intel_engine_types.h to avoid checkpatch
    warnings
v3: update headers in intel_sseu.h
v4: add const to some sseu_dev_info variables
    use sseu->eu_stride for EU stride calculations
v5: address review comments from Tvrtko and Daniele
v6: remove extra space in intel_sseu_get_subslices
    return the correct subslice enable in for_each_instdone
    add GEM_BUG_ON to ensure user doesn't pass invalid ss_mask size
    use printk formatted string for subslice mask
v7: remove string.h header and rebase

Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Acked-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: Stuart Summers <stuart.summers@intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190524154022.13575-6-stuart.summers@intel.com