vty: Use same prompt string format like in libosmocore

Ensures a single blank after the '#'. Use (config-foo) instead (foo)
for config nodes.
diff --git a/src/e1_input_vty.c b/src/e1_input_vty.c
index faaebd8..d99c853 100644
--- a/src/e1_input_vty.c
+++ b/src/e1_input_vty.c
@@ -268,7 +268,7 @@
 
 struct cmd_node e1inp_node = {
 	L_E1INP_NODE,
-	"%s(e1_input)#",
+	"%s(config-e1_input)# ",
 	1,
 };