soc: aspeed: lpc-ctrl: Fix probe error handling

gcc warns that a mising "flash" phandle node leads to undefined
behavior later:

drivers/soc/aspeed/aspeed-lpc-ctrl.c: In function 'aspeed_lpc_ctrl_probe':
drivers/soc/aspeed/aspeed-lpc-ctrl.c:201:18: error: '*((void *)&resm+8)' may be used uninitialized in this function [-Werror=maybe-uninitialized]

Only set the flash base and size if we find a phandle in the device
tree.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Andrew Jeffery <andrew@aj.id.au>
Reviewed-by: Vijay Khemka <vijaykhemka@fb.com>
Signed-off-by: Joel Stanley <joel@jms.id.au>

drivers/soc/aspeed/aspeed-lpc-ctrl.c

@@ -223,10 +223,11 @@ static int aspeed_lpc_ctrl_probe(struct platform_device *pdev)
 			dev_err(dev, "Couldn't address to resource for flash\n");
 			return rc;
 		}
+
+		lpc_ctrl->pnor_size = resource_size(&resm);
+		lpc_ctrl->pnor_base = resm.start;
 	}
 
-	lpc_ctrl->pnor_size = resource_size(&resm);
-	lpc_ctrl->pnor_base = resm.start;
 
 	dev_set_drvdata(&pdev->dev, lpc_ctrl);