mb/system76/gaze15: Add NB_ENAVDD to early_gpio_table

Fixes FSP not finding a valid framebuffer on reboots, which resulted in
a black screen when running the edk2 payload.

Change-Id: I946adb0657c07cf6c5a9aeb369e4fdfd8826abb2

src/mainboard/system76/gaze15/gpio.h

@@ -16,6 +16,7 @@
 static const struct pad_config early_gpio_table[] = {
 		PAD_CFG_GPI(GPP_C20, NONE, DEEP), // UART2_RXD
 		PAD_CFG_GPI(GPP_C21, NONE, DEEP), // UART2_TXD
+		PAD_CFG_NF(GPP_F19, NONE, DEEP, NF1), // NB_ENAVDD
 		PAD_CFG_TERM_GPO(DGPU_RST_N, 0, NONE, DEEP), // DGPU_RST#_PCH
 		PAD_CFG_TERM_GPO(DGPU_PWR_EN, 0, NONE, DEEP), // DGPU_PWR_EN
 };