Network debugging doesn't seem to work for PPP

I was testing PPP app and when try to enable network debugging, as shown below, nothing happens. I start investigating that, I remove **ninfo** ( app/netutils/pppd/ppp_config.h) and use **printf**, and works very well.
@acassis


- With printf

```
NuttShell (NSH) NuttX-12.0.0
nsh> pppd &
pppd [4:100]
nsh> tun fd:3
tty fd:4
ipcp init

AHDLC_TX - transmit frame, protocol 0xc021, length 4 offline 0

0x05 0x01 0x00 0x04

AHDLC_TX - transmit frame, protocol 0xc021, length 4 offline 1

0x05 0x02 0x00 0x04

chat: ATZ

chat: OK
```
- Without printf
```
NuttShell (NSH) NuttX-12.0.0
nsh> pppd &
pppd [4:100]
nsh> chat: ATZ

chat: OK
chat: cmd 1, arg ON

chat: cmd 4, arg 30

chat: AT+QACCM=0,0

chat: cmd 2, arg 3

chat: OK AT+CGDCONT=1,"IP","tim.br"
```