configs: orangepipc defconfig needs dtc for u-boot

As can be seen at
https://travis-ci.org/buildroot/buildroot-defconfig-testing/jobs/99518455,
the new Orange Pi PC defconfig fails to build due to DTC being missing
when building U-Boot. This commit adds the appropriate option to add
DTC as a dependency to U-Boot.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

configs/orangepipc_defconfig

@@ -24,6 +24,7 @@ BR2_TARGET_UBOOT_BOARDNAME="orangepi_pc"
 BR2_TARGET_UBOOT_CUSTOM_GIT=y
 BR2_TARGET_UBOOT_CUSTOM_REPO_URL="http://git.denx.de/u-boot.git"
 BR2_TARGET_UBOOT_CUSTOM_REPO_VERSION="4832e17787acb29734d895751bc7a594908aecc6"
+BR2_TARGET_UBOOT_NEEDS_DTC=y
 BR2_TARGET_UBOOT_FORMAT_CUSTOM=y
 BR2_TARGET_UBOOT_FORMAT_CUSTOM_NAME="u-boot-sunxi-with-spl.bin"
 BR2_PACKAGE_HOST_GENIMAGE=y