gianfar: Fix potential oops during OF address translation

gianfar driver may pass NULL pointer to the of_translate_address(),
which may lead to a kernel oops. Fix this by using of_iomap(), which
is also much simpler and shorter.
Signed-off-by: NAnton Vorontsov <avorontsov@mvista.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/gianfar.c

@@ -549,12 +549,8 @@ static int gfar_parse_group(struct device_node *np,
 		struct gfar_private *priv, const char *model)
 {
 	u32 *queue_mask;
-	u64 addr, size;
-
-	addr = of_translate_address(np,
-			of_get_address(np, 0, &size, NULL));
-	priv->gfargrp[priv->num_grps].regs = ioremap(addr, size);
 
+	priv->gfargrp[priv->num_grps].regs = of_iomap(np, 0);
 	if (!priv->gfargrp[priv->num_grps].regs)
 		return -ENOMEM;