cxgb4: Try and provide an RDMA CIQ per cpu

To allow for better scalability on systems with large core counts, we
will try and allocate enough RDMA Concentrator IQs and MSI/X vectors as
we have cores. If we cannot get enough MSI/X vectors, fall back to the
minimum required: 1 per adapter rx channel.

Also clean up cxgb_enable_msix() to make it readable and correct a bug
where the vectors are not correctly assigned if the driver doesn't get
the full amount requested.

Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Hariprasad Shenai <hariprasad@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>