configs/beaglebone_qt5: add overlay to defconfig

commit 8efc5dce98f9795d97b7a3452f9be4a774032379 added an overlay but
forgot to add it to the related defconfig.

Fixes: missing overlay data in image

Signed-off-by: Michael Nosthoff <buildroot@heine.tech>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

configs/beaglebone_qt5_defconfig

@@ -5,6 +5,7 @@ BR2_TOOLCHAIN_BUILDROOT_GLIBC=y
 BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_4_19=y
 BR2_TOOLCHAIN_BUILDROOT_CXX=y
 BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_EUDEV=y
+BR2_ROOTFS_OVERLAY="board/beaglebone/rootfs_overlay"
 BR2_ROOTFS_POST_BUILD_SCRIPT="board/beaglebone/post-build.sh"
 BR2_ROOTFS_POST_IMAGE_SCRIPT="support/scripts/genimage.sh"
 BR2_ROOTFS_POST_SCRIPT_ARGS="-c board/beaglebone/genimage.cfg"