env: Drop _ENTRY

This typedef does not need to be defined in the search.h header since it
is only used in one file (hashtable.c). Remove it from the header and
change it to a struct.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/search.h b/include/search.h
index 81745a9..c99648f 100644
--- a/include/search.h
+++ b/include/search.h
@@ -34,9 +34,6 @@
 	int flags;
 };
 
-/* Opaque type for internal use.  */
-struct _ENTRY;
-
 /*
  * Family of hash table handling functions.  The functions also
  * have reentrant counterparts ending with _r.  The non-reentrant
@@ -45,7 +42,7 @@
 
 /* Data type for reentrant functions.  */
 struct hsearch_data {
-	struct _ENTRY *table;
+	struct env_entry_node *table;
 	unsigned int size;
 	unsigned int filled;
 /*