bluetooth: increment BT_BUF_CMD_TX_COUNT

The extended advertising start procedure can consume both command
buffers in a single API call, resulting in `bt_le_create_conn_cancel`
being unable to claim a buffer to terminate the connection request.

Increase the command count if both extended advertising and Bluetooth
central are enabled in an application.

Signed-off-by: Jordan Yates <[email protected]>

Author: JordanYates

subsys/bluetooth/common/Kconfig

@@ -172,6 +172,7 @@ config BT_BUF_CMD_TX_SIZE
 
 config BT_BUF_CMD_TX_COUNT
 	int "Number of HCI command buffers"
+	default 3 if BT_EXT_ADV && BT_CENTRAL
 	default 2
 	range 2 64
 	help