usb: gadget: r8a66597: Add missing null check on return from platform_get_resource

The call to platform_get_resource can potentially return a NULL pointer
on failure, so add this check and return -EINVAL if it fails.

Fixes: c4144247 ("usb: gadget: R8A66597 peripheral controller support.")
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Addresses-Coverity: ("Dereference null return")
Link: https://lore.kernel.org/r/20210406184510.433497-1-colin.king@canonical.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/udc/r8a66597-udc.c

@@ -1849,6 +1849,8 @@ static int r8a66597_probe(struct platform_device *pdev)
 		return PTR_ERR(reg);
 
 	ires = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
+	if (!ires)
+		return -EINVAL;
 	irq = ires->start;
 	irq_trigger = ires->flags & IRQF_TRIGGER_MASK;