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/imx8mm_beacon_defconfig b/configs/imx8mm_beacon_defconfig
index fe9d230..6493dc8 100644
--- a/configs/imx8mm_beacon_defconfig
+++ b/configs/imx8mm_beacon_defconfig
@@ -30,7 +30,7 @@
 CONFIG_SPL_SEPARATE_BSS=y
 CONFIG_SPL_I2C_SUPPORT=y
 CONFIG_SPL_POWER=y
-CONFIG_SPL_WATCHDOG_SUPPORT=y
+CONFIG_SPL_WATCHDOG=y
 CONFIG_HUSH_PARSER=y
 CONFIG_SYS_PROMPT="u-boot=> "
 # CONFIG_CMD_EXPORTENV is not set