net/mlx5: re-indent generic probing function

net/mlx5: re-indent generic probing function

Since commit "net/mlx5: drop useless support for several Verbs ports"
removed an inner loop, mlx5_dev_spawn() is left with an unnecessary indent
level.

This patch eliminates a block, moves its local variables to function scope,
and re-indents its contents (diff best viewed with --ignore-all-space).

No functional impact.

Signed-off-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>
Reviewed-by: Xueming Li <xuemingl@mellanox.com>