Fix quantize_b_c function

Correctly compute the quantized coefficient index. This resolves
an enc/dec mismatch issue when the c function is in use.

Change-Id: I670b5a18310fa68c994f43b6a8bc9b0d8ff907ae
diff --git a/aom_dsp/quantize.c b/aom_dsp/quantize.c
index c82841a..0759c22 100644
--- a/aom_dsp/quantize.c
+++ b/aom_dsp/quantize.c
@@ -83,7 +83,7 @@
                        quant_shift_ptr[rc != 0]) >>
                       (16 - log_scale));  // quantization
 #endif  // CONFIG_AOM_QM
-        qcoeff_ptr[rc] = (tmp ^ coeff_sign) - coeff_sign;
+        qcoeff_ptr[rc] = (tmp32 ^ coeff_sign) - coeff_sign;
 #if CONFIG_AOM_QM
         const int dequant =
             (dequant_ptr[rc != 0] * iqm_ptr[rc] + (1 << (AOM_QM_BITS - 1))) >>