net/mlx5: Remove redundant check of mlx5_vhca_event_supported()

Since mlx5_vhca_event_supported() is called in mlx5_sf_dev_supported(),
remove the redundant call.

Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Reviewed-by: Shay Drory <shayd@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>