drm/nouveau/gpio/tu104: initial support

Appears to be compatible with GK104.
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

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

@@ -2439,6 +2439,7 @@ nv164_chipset = {
 	.name = "TU104",
 	.bios = nvkm_bios_new,
 	.devinit = tu104_devinit_new,
+	.gpio = gk104_gpio_new,
 	.ibus = gm200_ibus_new,
 	.pci = gp100_pci_new,
 	.top = gk104_top_new,