net/mlx5: mlx5e_hv_vhca_stats_create return type to void

Callers of this functions ignore its return value, as reported by
Wang Qing, in one of the return paths, it returns positive values.

Since return value is ignored anyways, void out the return type of the
function.

Reported-by: Wang Qing <wangqing@vivo.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>