drm/xe/uapi: Document DRM_XE_DEVICE_QUERY_HWCONFIG

Add a documentation on the content and format of when using query type
DRM_XE_DEVICE_QUERY_HWCONFIG. The list of keys can be found in IGT
under lib/intel_hwconfig_types.h.
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Acked-by: José Roberto de Souza <jose.souza@intel.com>
Acked-by: Mateusz Naklicki <mateusz.naklicki@intel.com>
Signed-off-by: Francois Dugast <francois.dugast@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

include/uapi/drm/xe_drm.h

@@ -537,6 +537,11 @@ struct drm_xe_device_query {
 #define DRM_XE_DEVICE_QUERY_MEM_REGIONS		1
 #define DRM_XE_DEVICE_QUERY_CONFIG		2
 #define DRM_XE_DEVICE_QUERY_GT_LIST		3
+	/*
+	 * Query type to retrieve the hardware configuration of the device
+	 * such as information on slices, memory, caches, and so on. It is
+	 * provided as a table of attributes (key / value).
+	 */
 #define DRM_XE_DEVICE_QUERY_HWCONFIG		4
 #define DRM_XE_DEVICE_QUERY_GT_TOPOLOGY		5
 #define DRM_XE_DEVICE_QUERY_ENGINE_CYCLES	6