configs/stm32f469_disco: add host {dosfs, m}tools

Commit 04a0094f0ef077 (configs/stm32f469_disco: fix kernel bootup) changed
the defconfig to build a vfat image, but forgot to add dosfstools/mtools
host utilities needed for this.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
(cherry picked from commit 6dd9e246a7b497819fd34595835d61c635d993f6)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

configs/stm32f469_disco_defconfig

@@ -19,5 +19,7 @@ BR2_TARGET_ROOTFS_EXT2_SIZE="32M"
 # BR2_TARGET_ROOTFS_TAR is not set
 BR2_TARGET_UBOOT=y
 BR2_TARGET_UBOOT_BOARD_DEFCONFIG="stm32f469-discovery"
+BR2_PACKAGE_HOST_DOSFSTOOLS=y
 BR2_PACKAGE_HOST_GENIMAGE=y
+BR2_PACKAGE_HOST_MTOOLS=y
 BR2_PACKAGE_HOST_OPENOCD=y