watchdog: it87_wdt: add IT8620E ID

This adds IT8620E chip ID to it87_wdt driver.
Such chip is often found on current Gigabyte motherboards, it is allegedly
custom made for this manufacturer.

Upon testing it looks like it has a 16-bit timer and cannot be reset via
game port (only via CIR), so it is similar to IT87{18,20,21,28,83} chips.

Tested on GA-F2A88XM-HD3P board.
Signed-off-by: Maciej S. Szmigiero <mail@maciej.szmigiero.name>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/watchdog/Kconfig

@@ -1008,8 +1008,8 @@ config IT87_WDT
 	tristate "IT87 Watchdog Timer"
 	depends on X86
 	---help---
-	  This is the driver for the hardware watchdog on the ITE IT8702,
-	  IT8712, IT8716, IT8718, IT8720, IT8721, IT8726 and IT8728
+	  This is the driver for the hardware watchdog on the ITE IT8620,
+	  IT8702, IT8712, IT8716, IT8718, IT8720, IT8721, IT8726 and IT8728
 	  Super I/O chips.
 
 	  If the driver does not work, then make sure that the game port in

drivers/watchdog/it87_wdt.c

@@ -12,7 +12,7 @@
  *		    http://www.ite.com.tw/
  *
  *	Support of the watchdog timers, which are available on
- *	IT8702, IT8712, IT8716, IT8718, IT8720, IT8721, IT8726,
+ *	IT8620, IT8702, IT8712, IT8716, IT8718, IT8720, IT8721, IT8726,
  *	IT8728 and IT8783.
  *
  *	This program is free software; you can redistribute it and/or
@@ -78,6 +78,7 @@
 
 /* Chip Id numbers */
 #define NO_DEV_ID	0xffff
+#define IT8620_ID	0x8620
 #define IT8702_ID	0x8702
 #define IT8705_ID	0x8705
 #define IT8712_ID	0x8712
@@ -630,6 +631,7 @@ static int __init it87_wdt_init(void)
 	case IT8726_ID:
 		max_units = 65535;
 		break;
+	case IT8620_ID:
 	case IT8718_ID:
 	case IT8720_ID:
 	case IT8721_ID: