net/mlx5e: Clear VF config when switching modes

Currently VF in LEGACY mode are not able to go up. Also in OFFLOADS
mode, when switching to it first time, VF can go up independently to
his representor, which is not expected.
Perform clearing of VF config when switching modes and set link state
to AUTO as default value. Also, when switching to OFFLOADS mode set
link state to DOWN, which allow VF link state to be controlled by its
REP.

Fixes: 1ab2068a ("net/mlx5: Implement vports admin state backup/restore")
Fixes: 556b9d16

 ("net/mlx5: Clear VF's configuration on disabling SRIOV")
Signed-off-by: Dmytro Linkin <dmitrolin@mellanox.com>
Signed-off-by: Roi Dayan <roid@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>