watchdog: Split WDT from SPL_WDT

Use CONFIG_IS_ENABLED(WDT) to permit use of WDT in SPL without DM,
while the full U-Boot can use rich DM/DT WDT driver.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Peng Fan <Peng.Fan@freescale.com>
Cc: Stefano Babic <sbabic@denx.de>
Tested-by: Heiko Schocher <hs@denx.de>
Tested-by: Suniel Mahesh <sunil.m@techveda.org>
diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index ee0ddff..de9bd87 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -169,4 +169,11 @@
 	  Intel Tangier SoC. If you're using a board with Intel Tangier
 	  SoC, say Y here.
 
+config SPL_WDT
+	bool "Enable driver model for watchdog timer drivers in SPL"
+	depends on SPL_DM
+	help
+	  Enable driver model for watchdog timer in SPL.
+	  This is similar to CONFIG_WDT in U-Boot.
+
 endmenu