Fix a memleak in CLPF.

The memleak appeared in eb5794da1659f87597291d84c2fbdfd89280065d.

Change-Id: Ifdd6d64aafa0d0ce4dfaf1844f594d5f843bf2e0

av1/common/clpf.c

diff --git a/av1/common/clpf.c b/av1/common/clpf.c
index 1ca60e0..f4dfa1f 100644
--- a/av1/common/clpf.c
+++ b/av1/common/clpf.c
@@ -168,6 +168,7 @@
 
     aom_free(cache);
     aom_free(cache_ptr);
+    aom_free(cache_dst);
   }
 
   return block_index;