drm/xe/uapi: Align on a common way to return arrays (gt)

The uAPI provides queries which return arrays of elements. As of now
the format used in the struct is different depending on which element
is queried. However, aligning on the new common pattern:

    struct drm_xe_query_Xs {
       __u32 num_Xs;
       struct drm_xe_X Xs[];
       ...
    }

... would mean bringing back the name "gts" which is avoided per commit
fca54ba12470 ("drm/xe/uapi: Rename gts to gt_list") so make an exception
for gt and leave gt_list. Also, this change removes "query" in the
name of struct drm_xe_query_gt as it is not returned from the query
IOCTL. There is no functional change.

v2: Leave gt_list (Matt Roper)

Signed-off-by: Francois Dugast <francois.dugast@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>