watchdog: Fix POST failure on ASUS P5N32-E SLI and similar boards

At present the module does not unset the NO_REBOOT bit upon shutdown, this
causes the BIOS to fail the POST once and reset. During the next boot it
displays the following error message:

***** Warning: System BOOT Fail *****
Your system last boot fail or POST interrupted.
Please enter setup to load default and reboot again.
Press F1 to continue, DEL to enter SETUP

With this patch the NO_REBOOT flag will be unset on shutdown and thus stop
this failure from occurring.

Tested on 'ASUS P5N32-E SLI with BIOS revision 1801' and
          'ASUS P5N32-E SLI PLUS with BIOS revision 1502'.
Signed-off-by: Mart Gerrits <mart1987@gmail.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

drivers/watchdog/nv_tco.c

@@ -458,7 +458,15 @@ static int __devexit nv_tco_remove(struct platform_device *dev)
 
 static void nv_tco_shutdown(struct platform_device *dev)
 {
+	u32 val;
+
 	tco_timer_stop();
+
+	/* Some BIOSes fail the POST (once) if the NO_REBOOT flag is not
+	 * unset during shutdown. */
+	pci_read_config_dword(tco_pci, MCP51_SMBUS_SETUP_B, &val);
+	val &= ~MCP51_SMBUS_SETUP_B_TCO_REBOOT;
+	pci_write_config_dword(tco_pci, MCP51_SMBUS_SETUP_B, val);
 }
 
 static struct platform_driver nv_tco_driver = {