Change "vp10" to "av1" in source code

Change-Id: Ifd0d08b97538dcc04227eceb6fb087224c760c59

aom_dsp/fwd_txfm.c

diff --git a/aom_dsp/fwd_txfm.c b/aom_dsp/fwd_txfm.c
index 68409f9..4aa448a 100644
--- a/aom_dsp/fwd_txfm.c
+++ b/aom_dsp/fwd_txfm.c
@@ -770,7 +770,7 @@
   output[1] = 0;
 }
 
-#if CONFIG_VPX_HIGHBITDEPTH
+#if CONFIG_AOM_HIGHBITDEPTH
 void aom_highbd_fdct4x4_c(const int16_t *input, tran_low_t *output,
                           int stride) {
   aom_fdct4x4_c(input, output, stride);
@@ -809,4 +809,4 @@
                               int stride) {
   aom_fdct32x32_1_c(input, out, stride);
 }
-#endif  // CONFIG_VPX_HIGHBITDEPTH
+#endif  // CONFIG_AOM_HIGHBITDEPTH