virtio_net: Fix missed rtnl_unlock

The rtnl_lock would stay locked if allocating promisc_allmulti failed.
Also changed the allocation to GFP_KERNEL.

Fixes: ff7c7d9f ("virtio_net: Remove command data from control_buf")
Reported-by: Eric Dumazet <edumaset@google.com>
Link: https://lore.kernel.org/netdev/CANn89iLazVaUCvhPm6RPJJ0owra_oFnx7Fhc8d60gV-65ad3WQ@mail.gmail.com/


Signed-off-by: Daniel Jurgens <danielj@nvidia.com>
Reviewed-by: Brett Creeley <brett.creeley@amd.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/20240515163125.569743-1-danielj@nvidia.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>