Revert "checkasm: vp9dsp: Benchmark the dc-only version of idct_idct separately"

This reverts commit 81d7f0bb.

Instead of just benchmarking dc separately, test all relevant subparts
(in the next commit).
Signed-off-by: Martin Storsjö <martin@martin.st>

tests/checkasm/vp9dsp.c

@@ -297,12 +297,6 @@ static void check_itxfm(void)
                 }
                 bench_new(dst, sz * SIZEOF_PIXEL, coef, sz * sz);
             }
-            if (txtp == 0 && tx != 4) {
-                if (check_func(dsp.itxfm_add[tx][txtp], "vp9_inv_%s_%dx%d_dc_add",
-                               txtp_types[txtp], sz, sz)) {
-                    bench_new(dst, sz * SIZEOF_PIXEL, coef, 1);
-                }
-            }
         }
     }
     report("itxfm");