samples: bluetooth: pbp_public_broadcast: Align ISO TX netbuf size

- Change netbuf buffer pool to use CONFIG_BT_CONN_TX_USER_DATA_SIZE to
  avoid inconsistency and have enough buffer room when sending ISO data

Signed-off-by: Vinit Mehta <[email protected]>

Author: VinitMehta7492

samples/bluetooth/pbp_public_broadcast_source/src/main.c

@@ -36,7 +36,8 @@
 
 NET_BUF_POOL_FIXED_DEFINE(tx_pool,
 			  (BROADCAST_ENQUEUE_COUNT * CONFIG_BT_BAP_BROADCAST_SRC_STREAM_COUNT),
-			  BT_ISO_SDU_BUF_SIZE(CONFIG_BT_ISO_TX_MTU), 8, NULL);
+			  BT_ISO_SDU_BUF_SIZE(CONFIG_BT_ISO_TX_MTU),
+			  CONFIG_BT_CONN_TX_USER_DATA_SIZE, NULL);
 
 static K_SEM_DEFINE(sem_broadcast_started, 0, 1);
 static K_SEM_DEFINE(sem_broadcast_stopped, 0, 1);