ns/gbproxy/sgsn: Update configs to use logging level lnssignal'

In libosmocore I34b8fde2955ecc010d1dcd9512e1bba9211e2c0d we introduced
a new log subsystem; enabel it in the related configs here

Change-Id: Ie3d178e68aa81d5636c87940074cb6582ac2f131
diff --git a/ns/osmo-ns.sns.cfg b/ns/osmo-ns.sns.cfg
index ad69f35..58d306e 100644
--- a/ns/osmo-ns.sns.cfg
+++ b/ns/osmo-ns.sns.cfg
@@ -31,6 +31,7 @@
  logging level ljibuf debug
  logging level lrspro debug
  logging level lns debug
+ logging level lnssignal debug
  logging level lbssgp debug
 log gsmtap 127.0.0.1
  logging filter all 0
@@ -59,6 +60,7 @@
  logging level ljibuf debug
  logging level lrspro debug
  logging level lns debug
+ logging level lnssignal debug
  logging level lbssgp debug
 !
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