drivers: atm: use native kernel's hex_to_bin() func

Signed-off-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Chas Williams <chas@cmf.nrl.navy.mil>
Cc: linux-atm-general@lists.sourceforge.net
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/atm/horizon.c

@@ -1645,10 +1645,8 @@ static int hrz_send (struct atm_vcc * atm_vcc, struct sk_buff * skb) {
     unsigned short d = 0;
     char * s = skb->data;
     if (*s++ == 'D') {
-      for (i = 0; i < 4; ++i) {
-	d = (d<<4) | ((*s <= '9') ? (*s - '0') : (*s - 'a' + 10));
-	++s;
-      }
+	for (i = 0; i < 4; ++i)
+		d = (d << 4) | hex_to_bin(*s++);
       PRINTK (KERN_INFO, "debug bitmap is now %hx", debug = d);
     }
   }