am335x: beagle/evm: add device tree overlay support

TI am33xx devices such as the BeagleBone devices have numerous cape options such
as screens some of which need overlays from the beginning so it makes sense to
enable evice tree overlays.

Signed-off-by: Peter Robinson <pbrobinson@gmail.com>
diff --git a/configs/am335x_evm_defconfig b/configs/am335x_evm_defconfig
index ff1e43f..3fe845c 100644
--- a/configs/am335x_evm_defconfig
+++ b/configs/am335x_evm_defconfig
@@ -46,3 +46,5 @@
 CONFIG_G_DNL_VENDOR_NUM=0x0451
 CONFIG_G_DNL_PRODUCT_NUM=0xd022
 CONFIG_RSA=y
+CONFIG_OF_LIBFDT=y
+CONFIG_OF_LIBFDT_OVERLAY=y