net/mlx5: E-Switch, Fix resetting of encap mode when entering switchdev

E-Switch encap mode is relevant only when in switchdev mode.
The RDMA driver can query the encap configuration via
mlx5_eswitch_get_encap_mode(). Make sure it returns the currently
used mode and not the set one.

This reverts the cited commit which reset the encap mode
on entering switchdev and fixes the original issue properly.

Fixes: 9a64144d ("net/mlx5: E-Switch, Fix default encap mode")
Signed-off-by: Paul Blakey <paulb@nvidia.com>
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Reviewed-by: Maor Dickman <maord@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>