net/mlx5e: Refactor mlx5e_rss_init() and mlx5e_rss_free() API's

Introduce code refactoring below:
1) Introduce single API for creating and destroying rss object,
   mlx5e_rss_create() and mlx5e_rss_destroy() respectively.
2) mlx5e_rss_create() constructs and initializes RSS object depends
   on a function new param enum mlx5e_rss_create_type. Callers (like
   rx_res.c) will no longer need to allocate RSS object via
   mlx5e_rss_alloc() and initialize it immediately via
   mlx5e_rss_init_no_tirs() or mlx5e_rss_init(), this will be done by
   a single call to mlx5e_rss_create(). Hence, mlx5e_rss_alloc() and
   mlx5e_rss_init_no_tirs() have been removed from rss.h file and became
   static functions.

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>