intel: indicate cmd_len in intel_msaa_state

Depending on GENs, cmd_len may change.
diff --git a/icd/intel/state.h b/icd/intel/state.h
index f5bb405..2f7572f 100644
--- a/icd/intel/state.h
+++ b/icd/intel/state.h
@@ -55,6 +55,7 @@
 
     /* 3DSTATE_MULTISAMPLE and 3DSTATE_SAMPLE_MASK */
     uint32_t cmd[6];
+    XGL_UINT cmd_len;
 };
 
 struct intel_blend_state {