drm/mcde: Fix handling of platform_get_irq() error

platform_get_irq() returns -ERRNO on error.  In such case comparison
to 0 would pass the check.

Fixes: 5fc537bf ("drm/mcde: Add new driver for ST-Ericsson MCDE")
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200827071107.27429-1-krzk@kernel.org

drivers/gpu/drm/mcde/mcde_drv.c

@@ -331,8 +331,8 @@ static int mcde_probe(struct platform_device *pdev)
 	}
 
 	irq = platform_get_irq(pdev, 0);
-	if (!irq) {
-		ret = -EINVAL;
+	if (irq < 0) {
+		ret = irq;
 		goto clk_disable;
 	}