mgw: Introduce test TC_crcx_osmux_257

Related: SYS#5987
Change-Id: I74e6c760e076fe2547b6297a54524255fb8b
diff --git a/mgw/osmo-mgw.cfg b/mgw/osmo-mgw.cfg
index 1c5cfce..417026e 100644
--- a/mgw/osmo-mgw.cfg
+++ b/mgw/osmo-mgw.cfg
@@ -44,7 +44,7 @@
   sdp audio-payload send-name
   conn-timeout 0
   loop 0
-  number endpoints 31
+  number endpoints 300
   allow-transcoding
   osmux off
   osmux bind-ip 127.0.0.1