net/wan/fsl_ucc_hdlc: fix unitialized variable warnings

net/wan/fsl_ucc_hdlc: fix unitialized variable warnings

This fixes the following compiler warnings:
drivers/net/wan/fsl_ucc_hdlc.c: In function 'ucc_hdlc_poll':
warning: 'skb' may be used uninitialized in this function
[-Wmaybe-uninitialized]
  skb->mac_header = skb->data - skb->head;

and

drivers/net/wan/fsl_ucc_hdlc.c: In function 'ucc_hdlc_probe':
drivers/net/wan/fsl_ucc_hdlc.c:1127:3: warning: 'utdm' may be used
uninitialized in this function [-Wmaybe-uninitialized]
   kfree(utdm);

Signed-off-by: Holger Brunck <[email protected]>
Cc: Zhao Qiang <[email protected]>
Signed-off-by: David S. Miller <[email protected]>