configs/rock5b: enable DHCP for eth0

Enable DHCP for eth0.
This is perfectly fine even for users that are not using the Ethernet
on the rock5b, as in that case, udhcpc will simply fork to background
without delaying the boot.

Signed-off-by: Niklas Cassel <cassel@kernel.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

configs/rock5b_defconfig

@@ -46,6 +46,7 @@ BR2_PACKAGE_HOST_DOSFSTOOLS=y
 BR2_PACKAGE_HOST_DTC=y
 BR2_PACKAGE_HOST_GENIMAGE=y
 BR2_PACKAGE_HOST_MTOOLS=y
+BR2_SYSTEM_DHCP="eth0"
 BR2_ROOTFS_POST_BUILD_SCRIPT="board/radxa/rock5b/post-build.sh"
 BR2_ROOTFS_POST_IMAGE_SCRIPT="support/scripts/genimage.sh"
 BR2_ROOTFS_POST_SCRIPT_ARGS="-c board/radxa/rock5b/genimage.cfg"