The kselftests doc mentions that a config file should be present "if a
test needs specific kernel config options enabled". This selftest
requires some kernel config, but no config file was provided.

We could say that a sub-target could use the parent's config file, but
the kselftests doc doesn't mention anything about that. Plus the
net/openvswitch target is the only net target without a config file.

Here is a new config file, which is a trimmed version of the net one,
with hopefully the minimal required kconfig on top of 'make defconfig'.

The Fixes tag points to the introduction of the net/openvswitch target,
just to help validating this target on stable kernels.

Fixes: 25f16c873fb1 ("selftests: add openvswitch selftest suite")
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Reviewed-by: Eelco Chaudron <echaudro@redhat.com>
Link: https://patch.msgid.link/20260710-net-sft-fix-containers-v1-2-a2915c294ef5@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>