Update s6lx9 microblaze default configuration

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

configs/s6lx9_microboard_defconfig

@@ -12,6 +12,5 @@ BR2_TARGET_ROOTFS_INITRAMFS=y
 BR2_LINUX_KERNEL=y
 BR2_LINUX_KERNEL_USE_CUSTOM_CONFIG=y
 BR2_LINUX_KERNEL_CUSTOM_CONFIG_FILE="board/avnet/s6lx9_microboard/lx9_mmu_defconfig"
-BR2_LINUX_KERNEL_DTS_FILE="board/avnet/s6lx9_microboard/lx9_mmu.dts"
-BR2_LINUX_KERNEL_IMAGE_TARGET_CUSTOM=y
-BR2_LINUX_KERNEL_IMAGE_TARGET_NAME="simpleImage.lx9_mmu"
+BR2_LINUX_KERNEL_USE_CUSTOM_DTS=y
+BR2_LINUX_KERNEL_CUSTOM_DTS_PATH="board/avnet/s6lx9_microboard/lx9_mmu.dts"