align buffers to avoid Segmentation fault

BUG=aomedia:579

Change-Id: I41731a71e25db429a78512a72afed10b6929da70

av1/encoder/rdopt.c

diff --git a/av1/encoder/rdopt.c b/av1/encoder/rdopt.c
index 1731b23..79fe13e 100644
--- a/av1/encoder/rdopt.c
+++ b/av1/encoder/rdopt.c
@@ -8504,8 +8504,8 @@
     int tmp_skip_txfm_sb;
     int64_t tmp_skip_sse_sb;
     int compound_type_cost[COMPOUND_TYPES];
-    uint8_t pred0[2 * MAX_SB_SQUARE];
-    uint8_t pred1[2 * MAX_SB_SQUARE];
+    DECLARE_ALIGNED(16, uint8_t, pred0[2 * MAX_SB_SQUARE]);
+    DECLARE_ALIGNED(16, uint8_t, pred1[2 * MAX_SB_SQUARE]);
     uint8_t *preds0[1] = { pred0 };
     uint8_t *preds1[1] = { pred1 };
     int strides[1] = { bw };