The commit cited below moved firmware flashing functionality from
mlxsw_spectrum to mlxsw_core, but did not adjust the Kconfig
dependencies. This makes it possible to have mlxsw_core as built-in and
mlxfw as a module. The mlxfw code is therefore not reachable from
mlxsw_core and firmware flashing fails:
# devlink dev flash pci/0000:01:00.0 file mellanox/mlxsw_spectrum-13.2008.1310.mfa2
devlink answers: Operation not supported