driver: watchdog: add sp805 watchdog support

sp805 is watchdog on some NXP layerscape SoCs, adding
it's driver. Configs CONFIG_WDT_SP805, CONFIG_WDT, CONFIG_CMD_WDT
needs to be enabled to use it.

Signed-off-by: Zhao Qiang <qiang.zhao@nxp.com>
Reviewed-by: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>
diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index f909d40..b01dbc4 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -103,6 +103,13 @@
 	   Select this to enable Orion watchdog timer, which can be found on some
 	   Marvell Armada chips.
 
+config WDT_SP805
+	bool "SP805 watchdog timer support"
+	depends on WDT
+	help
+	   Select this to enable SP805 watchdog timer, which can be found on some
+	   nxp layerscape chips.
+
 config WDT_CDNS
 	bool "Cadence watchdog timer support"
 	depends on WDT