Align frame_context to 16 bytes in TileData

BUG=aomedia:432

Change-Id: Ide94ffbf5ed0f25ac64892f02364b67cefa5fd15

av1/decoder/decoder.h

diff --git a/av1/decoder/decoder.h b/av1/decoder/decoder.h
index 7f09e7f..e05102d 100644
--- a/av1/decoder/decoder.h
+++ b/av1/decoder/decoder.h
@@ -51,7 +51,7 @@
   DECLARE_ALIGNED(16, tran_low_t, pvq_ref_coeff[OD_TXSIZE_MAX * OD_TXSIZE_MAX]);
 #endif
 #if CONFIG_EC_ADAPT
-  FRAME_CONTEXT tctx;
+  DECLARE_ALIGNED(16, FRAME_CONTEXT, tctx);
 #endif
 #if CONFIG_PALETTE
   DECLARE_ALIGNED(16, uint8_t, color_index_map[2][MAX_SB_SQUARE]);

av1/encoder/encoder.h

diff --git a/av1/encoder/encoder.h b/av1/encoder/encoder.h
index 6d3497f..5c4a6a6 100644
--- a/av1/encoder/encoder.h
+++ b/av1/encoder/encoder.h
@@ -289,7 +289,7 @@
   PVQ_QUEUE pvq_q;
 #endif
 #if CONFIG_EC_ADAPT
-  FRAME_CONTEXT tctx;
+  DECLARE_ALIGNED(16, FRAME_CONTEXT, tctx);
 #endif
 } TileDataEnc;