net/mlx5: use anonymous Direct Verbs allocator argument

net/mlx5: use anonymous Direct Verbs allocator argument

The mlx5_dev_spawn function defines an struct mlx5dv_ctx_allocators type
variable several hundred rows after it starts, with the only use it
being passed as a parameter to the mlx5_glue->dv_set_context_attr
function.
However, according to DPDK Coding Style Guidelines, variables should be
declared at the start of a block of code rather than in the middle.
Therefore, to improve the Coding Style, the variable is passed directly
to the function without declaring it before.

Signed-off-by: Michael Baum <michaelba@mellanox.com>
Acked-by: Matan Azrad <matan@mellanox.com>