irda: add missing BKL in irnet_ppp ioctl

One ioctl has been forgotten when the BKL was push down into irnet_ppp
ioctl function.
Signed-off-by: NThadeu Lima de Souza Cascardo <cascardo@holoscopio.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/irda/irnet/irnet_ppp.c

@@ -698,9 +698,11 @@ dev_irnet_ioctl(
 
       /* Query PPP channel and unit number */
     case PPPIOCGCHAN:
+      lock_kernel();
       if(ap->ppp_open && !put_user(ppp_channel_index(&ap->chan),
 						(int __user *)argp))
 	err = 0;
+      unlock_kernel();
       break;
     case PPPIOCGUNIT:
       lock_kernel();