Disable txmg when using daala transforms.

Change-Id: Ib38368d0aa7e13e53e8040c75a8564fbdb7646c7
diff --git a/configure b/configure
index 009de46..7ecc0ca 100755
--- a/configure
+++ b/configure
@@ -603,6 +603,7 @@
     fi
     if enabled daala_dct4 || enabled daala_dct8 || enabled daala_dct16 ||
         enabled daala_dct32 || enabled daala_dct64; then
+      disable_feature txmg
       disable_feature lgt
       enable_feature lowbitdepth
     fi