bts_ipaccess_nanobts.c: Remove unused variable.

This must have been obsoleted by the move to libosmo-abis.

GCC warning:
bts_ipaccess_nanobts.c: In function ‘ipaccess_drop_oml’:
bts_ipaccess_nanobts.c:509:21: warning: variable ‘line’ set but not used [-Wunused-but-set-variable]

openbsc/src/libbsc/bts_ipaccess_nanobts.c

@@ -506,13 +506,10 @@ void ipaccess_drop_rsl(struct gsm_bts_trx *trx)
 void ipaccess_drop_oml(struct gsm_bts *bts)
 {
 	struct gsm_bts_trx *trx;
-	struct e1inp_line *line;
 
 	if (!bts->oml_link)
 		return;
 
-	line = bts->oml_link->ts->line;
-
 	e1inp_sign_link_destroy(bts->oml_link);
 	bts->oml_link = NULL;