watchdog: Convert txx9wdt driver to watchdog framework

This patch converts txx9wdt driver to watchdog framework.
Also use devm_* APIs to save a few error handling code.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: Wolfram Sang <w.sang@pengutronix.de>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index e25a464..5d8cd69e1 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -1003,6 +1003,7 @@
 config TXX9_WDT
 	tristate "Toshiba TXx9 Watchdog Timer"
 	depends on CPU_TX39XX || CPU_TX49XX
+	select WATCHDOG_CORE
 	help
 	  Hardware driver for the built-in watchdog timer on TXx9 MIPS SoCs.