Remove unneeded memset on sign array

Change-Id: I21213ad3a8b9bd018927582ffa7eeab372aa7f9c

av1/decoder/decodetxb.c

diff --git a/av1/decoder/decodetxb.c b/av1/decoder/decodetxb.c
index d70340a..c6305e5 100644
--- a/av1/decoder/decodetxb.c
+++ b/av1/decoder/decodetxb.c
@@ -96,7 +96,6 @@
   memset(levels_buf, 0,
          sizeof(*levels_buf) *
              ((width + TX_PAD_HOR) * (height + TX_PAD_VER) + TX_PAD_END));
-  memset(signs, 0, sizeof(*signs) * seg_eob);
 
   (void)blk_row;
   (void)blk_col;