drm/nouveau/device/tegra: fix uninitialized IRQ number

nvkm_device_tegra_new initializes the irq member of the Tegra device
to -1 in order to signal that it is uninitialized. However,
nvkm_device_tegra_fini tests it against 0 to check whether an IRQ has
been allocated or not. This leads to free_irq being called on -1 during
device initialization.

Fix this by using 0 as the uninitialized value everywhere.
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nvkm/engine/device/tegra.c

@@ -255,7 +255,6 @@ nvkm_device_tegra_new(const struct nvkm_device_tegra_func *func,
 
 	tdev->func = func;
 	tdev->pdev = pdev;
-	tdev->irq = -1;
 
 	tdev->vdd = devm_regulator_get(&pdev->dev, "vdd");
 	if (IS_ERR(tdev->vdd)) {