drm/i915/doc: Convert drm_i915_query_topology_info comment to kerneldoc

This structure has a great comment describing the fields, but it's not
currently in kerneldoc form and does not show up in the generated
documentation.  Let's fix that and also clarify the description of what
"subslice" refers to on gen12 platforms and beyond and that "slice" is
no longer meaningful on Xe_HP and beyond.

Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Francisco Jerez <currojerez@riseup.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20220414192230.749771-1-matthew.d.roper@intel.com