Bluetooth: classic: Kconfig: set BT_RFCOMM_DLC_STACK_SIZE default 512

For the shell RFCOMM case, these is a stack overflow problem when do
disconnect, so need to increase the CONFIG_BT_RFCOMM_DLC_STACK_SIZE.
Set CONFIG_BT_RFCOMM_DLC_STACK_SIZE default 512.

Signed-off-by: Make Shi <make.shi@nxp.com>

Author: makeshi

subsys/bluetooth/host/classic/Kconfig

@@ -61,8 +61,7 @@ config BT_RFCOMM_TX_MAX
 
 config BT_RFCOMM_DLC_STACK_SIZE
 	int "Stack size of DLC for RFCOMM"
-	default 512 if BT_HFP_AG
-	default 256
+	default 512
 	help
 	  Stack size of DLC for RFCOMM. This is the context from which
 	  all data of upper layer are sent and disconnect