Rename SPL_WATCHDOG_SUPPORT to SPL_WATCHDOG

Rename this option so that CONFIG_IS_ENABLED can be used with it.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/mach-imx/mx6/Kconfig b/arch/arm/mach-imx/mx6/Kconfig
index a03eca8..d460268 100644
--- a/arch/arm/mach-imx/mx6/Kconfig
+++ b/arch/arm/mach-imx/mx6/Kconfig
@@ -314,7 +314,7 @@
 	select SPL_USB_GADGET if SPL
 	select SPL_USB_HOST_SUPPORT if SPL
 	select SPL_USB_SDP_SUPPORT if SPL
-	select SPL_WATCHDOG_SUPPORT if SPL
+	select SPL_WATCHDOG if SPL
 	select SUPPORT_SPL
 	imply CMD_DM