configs: stm32mp15: Enable WDT flags

This allows to enable WATCHDOG and WDT flags to
be able to reset the watchdog and to support watchdog driver
model.

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
diff --git a/configs/stm32mp15_trusted_defconfig b/configs/stm32mp15_trusted_defconfig
index 64ce86a..22ca23d 100644
--- a/configs/stm32mp15_trusted_defconfig
+++ b/configs/stm32mp15_trusted_defconfig
@@ -96,3 +96,5 @@
 CONFIG_USB_GADGET_VENDOR_NUM=0x0483
 CONFIG_USB_GADGET_PRODUCT_NUM=0x5720
 CONFIG_USB_GADGET_DWC2_OTG=y
+CONFIG_WDT=y
+CONFIG_WDT_STM32MP=y