Enable ext-tx by default

Change-Id: I30b1367b8f1417abb36f80ea634036af48afa0ae
diff --git a/configure b/configure
index ac6b1ad..03466d3 100755
--- a/configure
+++ b/configure
@@ -482,6 +482,7 @@
     soft_enable tile_groups
     soft_enable rect_tx
     soft_enable global_motion
+    soft_enable ext_tx
     soft_enable cdef
     soft_enable ec_adapt
     soft_enable new_tokenset