wdog: Add the watchdog driver for MX7ULP.

This driver implements the HW WATCHDOG functions. Which needs
to set CONFIG_HW_WATCHDOG to use them. This is disabled by default for
mx7ulp.

Use watchdog for reset cpu. Implement this in the driver.
Need to define CONFIG_ULP_WATCHDOG to build it.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Ye Li <ye.li@nxp.com>
Cc: Stefano Babic <sbabic@denx.de>
diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index e69de29..dbdaafc 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -0,0 +1,8 @@
+menu "WATCHDOG support"
+
+config ULP_WATCHDOG
+	bool "i.MX7ULP watchdog"
+	help
+	  Say Y here to enable i.MX7ULP watchdog driver.
+
+endmenu