sw_load: Specify the trx_nr for the software load

For the multi TRX setup we will need to specify the right trx->nr
to be able to flash the BTS. For the BS11 case we are ignoring the
additional argument.
diff --git a/openbsc/src/bs11_config.c b/openbsc/src/bs11_config.c
index d8819d3..8f6de8a 100644
--- a/openbsc/src/bs11_config.c
+++ b/openbsc/src/bs11_config.c
@@ -481,7 +481,7 @@
 		 * argument, so our swload_cbfn can distinguish
 		 * a safety load from a regular software */
 		if (file_is_readable(fname_safety))
-			rc = abis_nm_software_load(g_bts, fname_safety,
+			rc = abis_nm_software_load(g_bts, 0xff, fname_safety,
 						   win_size, param_forced,
 						   swload_cbfn, g_bts);
 		else