net/mlx5e: Refactor mlx5e_rss_set_rxfh() and mlx5e_rss_get_rxfh()

Initialize indirect table array with memcpy rather than for loop.
This change has made for two reasons:
1) To be consistent with the indirect table array init in
   mlx5e_rss_set_rxfh().
2) In general, prefer to use memcpy for array initializing rather than
   for loop.

Signed-off-by: Adham Faris <afaris@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>