cmd: env: add env load command

Add the new command env load to load the environment from
the current location gd->env_load_prio.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>

include/env.h

@@ -265,6 +265,13 @@ int env_set_default_vars(int nvars, char *const vars[], int flags);
  */
 int env_load(void);
 
+/**
+ * env_reload() - Re-Load the environment from current storage
+ *
+ * @return 0 if OK, -ve on error
+ */
+int env_reload(void);
+
 /**
  * env_save() - Save the environment to storage
  *