Revert "virtio-net: Don't print the compat warning for the default device"

This reverts commit 15757e8e.

Turns out there's a way to disable the default virtio-net device: pass
--network mode=none when running a VM.

Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
Link: https://lore.kernel.org/r/20230907171655.6996-2-alexandru.elisei@arm.com


Signed-off-by: Will Deacon <will@kernel.org>