intel: indicate cmd_len in intel_msaa_state

Depending on GENs, cmd_len may change.
diff --git a/icd/intel/state.c b/icd/intel/state.c
index 4ed8ff9..d93ebc7 100644
--- a/icd/intel/state.c
+++ b/icd/intel/state.c
@@ -343,6 +343,8 @@
 
     dw += cmd_len;
 
+    state->cmd_len = cmd_len + 2;
+
     /* 3DSTATE_SAMPLE_MASK */
     cmd = GEN_RENDER_CMD(3D, GEN6, 3DSTATE_SAMPLE_MASK);
     cmd_len = 2;