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/common/spl/spl.c b/common/spl/spl.c
index d1b072d..f6375b0 100644
--- a/common/spl/spl.c
+++ b/common/spl/spl.c
@@ -707,7 +707,7 @@
 	spl_board_init();
 #endif
 
-#if defined(CONFIG_SPL_WATCHDOG_SUPPORT) && CONFIG_IS_ENABLED(WDT)
+#if defined(CONFIG_SPL_WATCHDOG) && CONFIG_IS_ENABLED(WDT)
 	initr_watchdog();
 #endif