tty: serial: uartlite: Support probe deferral

Give uartlite a chance to be probed when IRQ controller will be finally
available and return potential -EPROBE_DEFER as-is. The condition "<="
has been changed to "<" to follow the recommendation in the header of
platform_get_irq().

Signed-off-by: Alexander Sverdlin <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/tty/serial/uartlite.c

···
 		return -ENODEV;
 
 	irq = platform_get_irq(pdev, 0);
-	if (irq <= 0)
-		return -ENXIO;
+	if (irq < 0)
+		return irq;
 
 	pdata->clk = devm_clk_get(&pdev->dev, "s_axi_aclk");
 	if (IS_ERR(pdata->clk)) {