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/seeed_npi_imx6ull_defconfig b/configs/seeed_npi_imx6ull_defconfig
index 46daa03..73560ff 100644
--- a/configs/seeed_npi_imx6ull_defconfig
+++ b/configs/seeed_npi_imx6ull_defconfig
@@ -25,7 +25,7 @@
 CONFIG_SPL_NAND_SUPPORT=y
 CONFIG_SPL_USB_HOST_SUPPORT=y
 CONFIG_SPL_USB_GADGET=y
-CONFIG_SPL_WATCHDOG_SUPPORT=y
+CONFIG_SPL_WATCHDOG=y
 CONFIG_CMD_MEMTEST=y
 CONFIG_CMD_DM=y
 CONFIG_CMD_GPIO=y