gallium: Fix MSVC compiler warnings.

src/mesa/pipe/softpipe/sp_state_sampler.c

@@ -30,6 +30,10 @@
  */
 
 #include "pipe/p_util.h"
+
+#include "pipe/draw/draw_context.h"
+
+#include "sp_context.h"
 #include "sp_context.h"
 #include "sp_state.h"
 #include "sp_texture.h"