cnat: explicit BIHASH_USE_HEAP setting

The session db (bihash_40_56_t) was inheriting BIHASH_USE_HEAP=1 from
vppinfra/bihash_24_8.h through a convoluted set of #includes. Set
BIHASH_USE_HEAP in cnat_bihash.h, to avoid a surprise long after
anyone remembers the story.

Type: improvement

Signed-off-by: Dave Barach <dave@barachs.net>
Change-Id: I8aa3be09b306fc99ba0b6baa5096a0a6829a8951
diff --git a/src/plugins/cnat/cnat_bihash.h b/src/plugins/cnat/cnat_bihash.h
index a148ad5..c488e61 100644
--- a/src/plugins/cnat/cnat_bihash.h
+++ b/src/plugins/cnat/cnat_bihash.h
@@ -20,12 +20,14 @@
 #undef BIHASH_KVP_AT_BUCKET_LEVEL
 #undef BIHASH_LAZY_INSTANTIATE
 #undef BIHASH_BUCKET_PREFETCH_CACHE_LINES
+#undef BIHASH_USE_HEAP
 
 #define BIHASH_TYPE			   _40_56
 #define BIHASH_KVP_PER_PAGE 2
 #define BIHASH_KVP_AT_BUCKET_LEVEL 1
 #define BIHASH_LAZY_INSTANTIATE 1
 #define BIHASH_BUCKET_PREFETCH_CACHE_LINES 2
+#define BIHASH_USE_HEAP			   1
 
 #ifndef __included_bihash_40_56_h__
 #define __included_bihash_40_56_h__