[965] Flush icache on new batch, not just new context.

This is required since our buffer manager may now move our
instruction-containing buffers at any batchbuffer emit.
diff --git a/src/mesa/drivers/dri/i965/brw_misc_state.c b/src/mesa/drivers/dri/i965/brw_misc_state.c
index 8277da7..450d62c 100644
--- a/src/mesa/drivers/dri/i965/brw_misc_state.c
+++ b/src/mesa/drivers/dri/i965/brw_misc_state.c
@@ -394,7 +394,7 @@
 const struct brw_tracked_state brw_pipe_control = {
    .dirty = {
       .mesa = 0,
-      .brw = BRW_NEW_CONTEXT,
+      .brw = BRW_NEW_BATCH,
       .cache = 0
    },
    .update = upload_pipe_control