nrhw20: fix Huawei modem startup timing

- Length power off phase to 130ms from 30ms to conform requirements

board/nm/nrhw20/board.c

@@ -619,24 +619,35 @@ static void init_pcie_slot(void)
 
 static void init_gsm(void)
 {
+	/*
+	 * Perform power up sequence for Huawei ME909s.
+	 *
+	 * Modem is initially disabled and does not start automatically.
+	 * Enable power and start modem by "pressing" POWER_ON_OFF input for 1.0s.
+	 *
+	 * References:
+	 *  - HUAWEI ME909s Series LTE LGA Module Hardware Guide, Issue 02, Date 2016-02-20
+	 *    3.3.2 Power Supply VBAT Interface
+	 *    3.4.2 Power-on/off Pin, Figure 3.7
+	 */
+
+	/* TODO: Keep Power-On and use GSM Modem Reset Signal to restart */
+
 	REQUEST_AND_SET_GPIO(NETBIRD_GPIO_RST_GSM);	/* Assert reset (active high) */
 	REQUEST_AND_CLEAR_GPIO(NETBIRD_GPIO_PWR_GSM);	/* Keep power switch inactive (released) */
 
 	da9063_set_gpio(PMIC_GSM_SUPPLY_EN_IO, 0);	/* Switch GSM Supply off */
-	mdelay(30);					/* Give time to discharge supply */
+	mdelay(30+100);					/* Give time to discharge supply */
+							/* Keep of for 100ms, #3.3.2 */
 
 	da9063_set_gpio(PMIC_GSM_SUPPLY_EN_IO, 1);	/* Enable GSM supply */
 	mdelay(10);
 
-	gpio_set_value(NETBIRD_GPIO_RST_GSM, 0);	/* Take modem out of reset. */
+	gpio_set_value(NETBIRD_GPIO_RST_GSM, 0);	/* Take modem out of reset */
-	mdelay(300);					/* Wait 300ms until modem can handle power request */
+	mdelay(300);					/* Wait for power to stabilizy, #3.4.2 */
 
-	/*
-	 * Do power up sequence.
-	 * The ME909 has a special power up sequence where we have to pull PWR for > 1s but < 7s (see manual)
-	 */
-	gpio_set_value(NETBIRD_GPIO_PWR_GSM, 1);
 	/* TODO: Defer to late_init, so that we don't block boot */
+	gpio_set_value(NETBIRD_GPIO_PWR_GSM, 1);	/* Generate power on event, #3.4.2 */
 	mdelay(1200);
 	gpio_set_value(NETBIRD_GPIO_PWR_GSM, 0);
 }