configs: via_imx6_vab820: correct genimage dependencies

The genimage configuration creates a vfat filesystem, so ensure we have
dosfstools / mtools built for the host.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

configs/via_imx6_vab820_defconfig

@@ -27,5 +27,7 @@ BR2_TARGET_UBOOT_FORMAT_IMX=y
 # Filesystem
 BR2_TARGET_ROOTFS_EXT2=y
 BR2_TARGET_ROOTFS_EXT2_4=y
+BR2_PACKAGE_HOST_DOSFSTOOLS=y
 BR2_PACKAGE_HOST_GENIMAGE=y
+BR2_PACKAGE_HOST_MTOOLS=y
 BR2_ROOTFS_POST_IMAGE_SCRIPT="board/via/imx6_vab820/post-image.sh"