drm/nouveau/gpio: check function 76 in the power check as well

Added GPIO is "Power Alert". It's uncertain if this
GPIO is set on GPU initialization or only if a change is detected by the
GPU at runtime.

This GPIO can be found on Tesla and sometimes on Fermi GPUs.

Untested, wrote according to documentation.
Signed-off-by: Mark Menzynski <mmenzyns@redhat.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/include/nvkm/subdev/bios/gpio.h

@@ -8,6 +8,7 @@ enum dcb_gpio_func_name {
 	DCB_GPIO_THERM_EXT_POWER_EVENT = 0x10,
 	DCB_GPIO_TVDAC1 = 0x2d,
 	DCB_GPIO_FAN_SENSE = 0x3d,
+	DCB_GPIO_POWER_ALERT = 0x4c,
 	DCB_GPIO_EXT_POWER_LOW = 0x79,
 	DCB_GPIO_LOGO_LED_PWM = 0x84,
 	DCB_GPIO_UNUSED = 0xff,

drivers/gpu/drm/nouveau/nvkm/subdev/gpio/base.c

@@ -185,6 +185,7 @@ static const struct dmi_system_id gpio_reset_ids[] = {
 
 static enum dcb_gpio_func_name power_checks[] = {
 	DCB_GPIO_THERM_EXT_POWER_EVENT,
+	DCB_GPIO_POWER_ALERT,
 	DCB_GPIO_EXT_POWER_LOW,
 };