mfd: lpc_ich: Do not create iTCO watchdog when WDAT table exists

ACPI WDAT table is the preferred way to use hardware watchdog over the
native iTCO_wdt. Windows only uses this table for its hardware watchdog
implementation so we should be relatively safe to trust it has been
validated by OEMs

Prevent iTCO watchdog creation if we detect that there is ACPI WDAT table.
Signed-off-by: NMika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: NGuenter Roeck <linux@roeck-us.net>
Acked-by: NLee Jones <lee.jones@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/mfd/lpc_ich.c

@@ -984,6 +984,10 @@ static int lpc_ich_init_wdt(struct pci_dev *dev)
 	int ret;
 	struct resource *res;
 
+	/* If we have ACPI based watchdog use that instead */
+	if (acpi_has_watchdog())
+		return -ENODEV;
+
 	/* Setup power management base register */
 	pci_read_config_dword(dev, priv->abase, &base_addr_cfg);
 	base_addr = base_addr_cfg & 0x0000ff80;