RDMA/mlx4: Initialize ib_spec on the stack

Initialize ib_spec on the stack before using it, otherwise we will have
garbage values that will break creating default rules with invalid parsing
error.

Fixes: a37a1a42

 ("IB/mlx4: Add mechanism to support flow steering over IB links")
Link: https://lore.kernel.org/r/20200413132235.930642-1-leon@kernel.org
Signed-off-by: Alaa Hleihel <alaa@mellanox.com>
Reviewed-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>