block-mount: drop package, ubox now does the job for us

package/block-mount/Config.in

package/block-mount/Makefile

package/block-mount/files/10-swap

package/block-mount/files/20-fsck

package/block-mount/files/40-mount

package/block-mount/files/50_determine_usb_root

package/block-mount/files/55_determine_extroot_sysupgrade

package/block-mount/files/60_pivot_usb_root

package/block-mount/files/block.sh

package/block-mount/files/extmount.sh

package/block-mount/files/fsck.sh

package/block-mount/files/fstab.config

package/block-mount/files/fstab.init

package/block-mount/files/mount.sh