tests/checkasm/vp8dsp: Use correct function pointer type

Forgotten in a54e53a1c428299b19c7b4e2b66d01c0482c41dd.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

tests/checkasm/vp8dsp.c

@@ -269,7 +269,8 @@ static void check_mc(void)
     LOCAL_ALIGNED_16(uint8_t, dst1, [16 * 16]);
     VP8DSPContext d;
     int type, k, dx, dy;
-    declare_func_emms(AV_CPU_FLAG_MMX, void, uint8_t *, ptrdiff_t, uint8_t *, ptrdiff_t, int, int, int);
+    declare_func_emms(AV_CPU_FLAG_MMX, void, uint8_t *, ptrdiff_t,
+                      const uint8_t *, ptrdiff_t, int, int, int);
 
     ff_vp78dsp_init(&d);