env: Add a loadaddr env handler

Remove the hard-coded loadaddr handler and use a callback instead

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>
diff --git a/include/env_callback.h b/include/env_callback.h
index 2f5048f..bb398ec 100644
--- a/include/env_callback.h
+++ b/include/env_callback.h
@@ -41,6 +41,7 @@
 #define ENV_CALLBACK_LIST_STATIC ENV_CALLBACK_VAR ":callbacks," \
 	"baudrate:baudrate," \
 	"bootfile:bootfile," \
+	"loadaddr:loadaddr," \
 	CONFIG_ENV_CALLBACK_LIST_STATIC
 
 struct env_clbk_tbl {