Kconfig: Convert CONFIG_IMX_WATCHDOG to Kconfig

Move this option to Kconfig and tidy up the config file of eight
boards which use it.

Signed-off-by: Xiaoliang Yang <xiaoliang.yang_1@nxp.com>
diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index d545b3e..02f4e1e 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -111,4 +111,11 @@
 	   Select this to enable Xilinx Axi watchdog timer, which can be found on some
 	   Xilinx Microblaze Platforms.
 
+config IMX_WATCHDOG
+	bool "Enable Watchdog Timer support for IMX and LSCH2 of NXP"
+	select HW_WATCHDOG
+	help
+	   Select this to enable the IMX and LSCH2 of Layerscape watchdog
+	   driver.
+
 endmenu