gprs: Increase NS_ALLOC_SIZE to 3k

2k can be insufficient when responding with a STATUS message to a long LLC
packet because the original message is included in the STATUS.

Change-Id: I6f76751cfadf61e87ce4367a38907083e1c98562
Ticket: SYS#2967
Sponsored-by: On-Waves ehf
diff --git a/include/osmocom/gprs/gprs_ns.h b/include/osmocom/gprs/gprs_ns.h
index 7c3b23c..130d8c0 100644
--- a/include/osmocom/gprs/gprs_ns.h
+++ b/include/osmocom/gprs/gprs_ns.h
@@ -23,7 +23,8 @@
 	"Alive Timer (Tns-alive) timeout\n"			\
 	"Alive Timer (Tns-alive) number of retries\n"
 
-#define NS_ALLOC_SIZE	2048
+/* Educated guess - LLC user payload is 1500 bytes plus possible headers */
+#define NS_ALLOC_SIZE	3072
 #define NS_ALLOC_HEADROOM 20
 
 enum ns_timeout {