samples: echo_server: increase sys workqueue stack

For nrf5340 with 802.15.4 system work queue stack size was too small.

Signed-off-by: Andrzej Kuros <[email protected]>

Author: ankuns

samples/net/sockets/echo_server/overlay-802154.conf

@@ -14,3 +14,5 @@ CONFIG_NET_L2_IEEE802154_SHELL=y
 CONFIG_NET_L2_IEEE802154_LOG_LEVEL_INF=y
 
 CONFIG_NET_CONFIG_IEEE802154_CHANNEL=26
+
+CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=2048