samples: net: mqtt: Fix stack overflow

Increase network thread stack size to resolve
overflow issue observed during WPA3 connection.

Fixes SHEL-3748.

Signed-off-by: Triveni Danda <[email protected]>

Author: D-Triveni

samples/net/mqtt/boards/nrf54l15dk_nrf54l15_cpuapp.conf

@@ -80,6 +80,7 @@ CONFIG_NRF70_IRQ_WQ_STACK_SIZE=1024
 CONFIG_NRF70_BH_WQ_STACK_SIZE=2300
 CONFIG_SHELL_STACK_SIZE=4400
 CONFIG_ISR_STACK_SIZE=512
+CONFIG_MQTT_SAMPLE_NETWORK_THREAD_STACK_SIZE=5000
 
 # Heap sizes
 CONFIG_HEAP_MEM_POOL_IGNORE_MIN=y