[misdn] Add option to automatically release layer2 on exit

Patch by Andreas Eversberg to automatically release
layer2 on exit of the application. Made the naming of
the variables consistent (only release_l2 and not both
release_l2 and l2_release).
diff --git a/include/openbsc/e1_input.h b/include/openbsc/e1_input.h
index b717c61..db565bf 100644
--- a/include/openbsc/e1_input.h
+++ b/include/openbsc/e1_input.h
@@ -145,7 +145,7 @@
 struct subch_mux *e1inp_get_mux(u_int8_t e1_nr, u_int8_t ts_nr);
 
 /* e1_config.c */
-int e1_config(struct gsm_bts *bts, int cardnr);
+int e1_config(struct gsm_bts *bts, int cardnr, int release_l2);
 int ia_config(struct gsm_bts *bts);
 int ipaccess_setup(struct e1inp_line *line);