net/mlx5: E-switch, Coverity: overlapping copy

When a capability is set via port function caps callbacks, a memcpy() is
performed in which the source and the target are the same address, e.g.:
the copy is redundant. Hence, Remove it.
Discovered by Coverity.

Fixes: 7db98396 ("net/mlx5: E-Switch, Implement devlink port function cmds to control RoCE")
Fixes: e5b9642a ("net/mlx5: E-Switch, Implement devlink port function cmds to control migratable")
Signed-off-by: Shay Drory <shayd@nvidia.com>
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>