board: sl28: enable SoC watchdog support

The SoC provides two additional watchdogs integrated in the SoC. Enable
support for these.

Signed-off-by: Michael Walle <michael@walle.cc>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>

configs/kontron_sl28_defconfig

@@ -110,6 +110,7 @@ CONFIG_USB_GADGET_DOWNLOAD=y
 # CONFIG_WATCHDOG_AUTOSTART is not set
 CONFIG_WDT=y
 CONFIG_WDT_SL28CPLD=y
+CONFIG_WDT_SP805=y
 CONFIG_OF_LIBFDT_ASSUME_MASK=0x0
 CONFIG_OF_LIBFDT_OVERLAY=y
 CONFIG_EFI_SET_TIME=y