v1.7.0

This release bumps the Linux kernel to 4.19.25. This change had an impact on how
the WiFi regulatory database gets loaded into the kernel. Instead of building it
into the kernel as previously done, the kernel loads it on demand. This requires
that all WiFi drivers be built as kernel modules so that the database isn't
loaded before the root filesystem is mounted. If you made a custom system and
see boot errors about not being able to load the regulatory database, this is
the problem.

A known bug with the Raspberry Pi Zero USB gadget interface is that it sometimes
doesn't load on Linux systems. Moving the gadget drivers to kernel modules seems
to work around this but it takes longer to load the gadget interface.

• Updated dependencies
  • nerves_system_br v1.7.0
  • Linux 4.19.25 with patches from the Raspberry Pi Foundation