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/configs/mx6slevk_spl_defconfig b/configs/mx6slevk_spl_defconfig
index c67eb4b..ed173a8 100644
--- a/configs/mx6slevk_spl_defconfig
+++ b/configs/mx6slevk_spl_defconfig
@@ -22,7 +22,7 @@
 CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_SPL_FS_EXT4=y
 CONFIG_SPL_I2C_SUPPORT=y
-CONFIG_SPL_WATCHDOG_SUPPORT=y
+CONFIG_SPL_WATCHDOG=y
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_BOOTZ=y
 CONFIG_CMD_GPIO=y