configs: sama5d2_ptc_ek: add fdt overlay support

Add commands for fdt overlay merging. This is required for the boot scripts
that detect PDAs and apply specific overlays to the DTB passed on to kernel.

Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
diff --git a/configs/sama5d2_ptc_ek_mmc_defconfig b/configs/sama5d2_ptc_ek_mmc_defconfig
index 047a7ec..60df0f0 100644
--- a/configs/sama5d2_ptc_ek_mmc_defconfig
+++ b/configs/sama5d2_ptc_ek_mmc_defconfig
@@ -67,3 +67,4 @@
 CONFIG_W1_GPIO=y
 CONFIG_W1_EEPROM=y
 CONFIG_W1_EEPROM_DS24XXX=y
+CONFIG_OF_LIBFDT_OVERLAY=y