atm: fix improper return value

It returns variable "error" when ioremap_nocache() returns a NULL
pointer. The value of "error" is 0 then, which will mislead the callers
to believe that there is no error. This patch fixes the bug, returning
"-ENOMEM".

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=189021

Signed-off-by: Pan Bian <bianpan2016@163.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/atm/eni.c

@@ -1727,7 +1727,7 @@ static int eni_do_init(struct atm_dev *dev)
 		printk("\n");
 		printk(KERN_ERR DEV_LABEL "(itf %d): can't set up page "
 		    "mapping\n",dev->number);
-		return error;
+		return -ENOMEM;
 	}
 	eni_dev->ioaddr = base;
 	eni_dev->base_diff = real_base - (unsigned long) base;