Move daala_fdst4() / daala_idst4() into daala_tx.c.

This commit has no impact on metrics.

Change-Id: I85007ef966b9aab4545499016ed68ab5c96a417a

av1/common/daala_tx.c

diff --git a/av1/common/daala_tx.c b/av1/common/daala_tx.c
index 9ad6388..8f93645 100644
--- a/av1/common/daala_tx.c
+++ b/av1/common/daala_tx.c
@@ -4124,3 +4124,21 @@
   od_bin_idct4(x, 1, y);
   for (i = 0; i < 4; i++) output[i] = (tran_low_t)x[i];
 }
+
+void daala_fdst4(const tran_low_t *input, tran_low_t *output) {
+  int i;
+  od_coeff x[4];
+  od_coeff y[4];
+  for (i = 0; i < 4; i++) x[i] = (od_coeff)input[i];
+  od_bin_fdst4(y, x, 1);
+  for (i = 0; i < 4; i++) output[i] = (tran_low_t)y[i];
+}
+
+void daala_idst4(const tran_low_t *input, tran_low_t *output) {
+  int i;
+  od_coeff x[4];
+  od_coeff y[4];
+  for (i = 0; i < 4; i++) y[i] = input[i];
+  od_bin_idst4(x, 1, y);
+  for (i = 0; i < 4; i++) output[i] = (tran_low_t)x[i];
+}