qed: RoCE doesn't need to use SRC

As RoCE doesn't need to use the SRC, allocating ILT memory
on behalf of RoCE is wasting available ILT lines.

Signed-off-by: Yuval Mintz <Yuval.Mintz@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>