intel: Add platform gpu thread limits

Set max number of threads for Sandybridge, Ivybridge and Haswell
and their various gt configurations.
diff --git a/icd/intel/gpu.h b/icd/intel/gpu.h
index 5df7c39..4199730 100644
--- a/icd/intel/gpu.h
+++ b/icd/intel/gpu.h
@@ -50,6 +50,9 @@
     char *path;         /* path to the render or legacy node, or NULL */
     int gen_opaque;     /* always read with intel_gpu_gen() */
     int gt;
+    int max_vs_threads;
+    int max_gs_threads;
+    int max_fs_threads;
 
     XGL_GPU_SIZE max_batch_buffer_size;
     XGL_UINT batch_buffer_reloc_count;