python3-setuptools-scm: add python3-toml dep

Fixes:
pkg_resources.DistributionNotFound: The 'toml' distribution was not
found and is required by setuptools-scm

Signed-off-by: Tim Orling <timothy.t.orling@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>