stm32mp1: activate OF_BOARD_SETUP and FDT_FIXUP_PARTITIONS

Update kernel MTD partition in device tree with U-Boot information.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
diff --git a/configs/stm32mp15_optee_defconfig b/configs/stm32mp15_optee_defconfig
index 83b0b03..a205f47 100644
--- a/configs/stm32mp15_optee_defconfig
+++ b/configs/stm32mp15_optee_defconfig
@@ -104,3 +104,4 @@
 CONFIG_USB_GADGET_VENDOR_NUM=0x0483
 CONFIG_USB_GADGET_PRODUCT_NUM=0x5720
 CONFIG_USB_GADGET_DWC2_OTG=y
+CONFIG_FDT_FIXUP_PARTITIONS=y