net/mlx5e: Clean up and fix error flows in mlx5e_alloc_rq

Although mlx5e_rq_free_shampo can be called unconditionally, it belongs
to case MLX5_WQ_TYPE_LINKED_LIST_STRIDING_RQ. Move it there to allow to
add more init/cleanup actions to the striding RQ case.

If xdp_rxq_info_reg_mem_model fails, don't forget to destroy the page
pool.

Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Reviewed-by: Saeed Mahameed <saeedm@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>