MTDA 0.31

What's Changed

• debian: do not call mtda-systemd-helper when running in chroot by @chombourger in #399
• meta-isar: images: make LAVA an optional feature by @chombourger in #400
• Add usbsdmux support by @jan-kiszka in #402
• check if the platform has any udc instances to avoid exception by @chombourger in #401

Full Changelog: v0.30...v0.31