gallium: add pipe_transfer_usage for z/s only mappings

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5338>
diff --git a/src/gallium/include/pipe/p_defines.h b/src/gallium/include/pipe/p_defines.h
index d82ffcd..88e65ca 100644
--- a/src/gallium/include/pipe/p_defines.h
+++ b/src/gallium/include/pipe/p_defines.h
@@ -353,6 +353,16 @@
    PIPE_TRANSFER_THREAD_SAFE = 1 << 15,
 
    /**
+    * Map only the depth aspect of a resource
+    */
+   PIPE_TRANSFER_DEPTH_ONLY = 1 << 16,
+
+   /**
+    * Map only the stencil aspect of a resource
+    */
+   PIPE_TRANSFER_STENCIL_ONLY = 1 << 17,
+
+   /**
     * This and higher bits are reserved for private use by drivers. Drivers
     * should use this as (PIPE_TRANSFER_DRV_PRV << i).
     */