net: zynq_gem: Do not return -ENOSYS on success

The .read_rom_hwaddr net_ops hook does not check the return value, which
is why it was never caught that we are currently returning 0 if the
read_rom_hwaddr function return -ENOSYS and -ENOSYS otherwise.

In this case we can simplify this by just returning the result of the
function.

Signed-off-by: Olliver Schinagl <oliver@schinagl.nl>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
Acked-by: Michal Simek <michal.simek@xilinx.com>

drivers/net/zynq_gem.c

@@ -587,14 +587,12 @@ __weak int zynq_board_read_rom_ethaddr(unsigned char *ethaddr)
 
 static int zynq_gem_read_rom_mac(struct udevice *dev)
 {
-	int retval;
 	struct eth_pdata *pdata = dev_get_platdata(dev);
 
-	retval = zynq_board_read_rom_ethaddr(pdata->enetaddr);
-	if (retval == -ENOSYS)
-		retval = 0;
+	if (!pdata)
+		return -ENOSYS;
 
-	return retval;
+	return zynq_board_read_rom_ethaddr(pdata->enetaddr);
 }
 
 static int zynq_gem_miiphy_read(struct mii_dev *bus, int addr,