env_callback: Mark find_env_callback as static

This is not called outside of env_callback.c so mark static, remove from
<env_callback.h>

Cc: Joe Hershberger <joe.hershberger@ni.com>
Signed-off-by: Tom Rini <trini@ti.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>

common/env_callback.c

@@ -31,7 +31,7 @@ DECLARE_GLOBAL_DATA_PTR;
 /*
  * Look up a callback function pointer by name
  */
-struct env_clbk_tbl *find_env_callback(const char *name)
+static struct env_clbk_tbl *find_env_callback(const char *name)
 {
 	struct env_clbk_tbl *clbkp;
 	int i;

include/env_callback.h

@@ -67,7 +67,6 @@ struct env_clbk_tbl {
 		int flags);
 };
 
-struct env_clbk_tbl *find_env_callback(const char *);
 void env_callback_init(ENTRY *var_entry);
 
 /*