Driver was relying on an older DPIO API, which provided a CPU-affine DPIO
in case it was called with preemption disabled.

Since this is no longer the case, save the CPU-affine DPIO in per-cpu
private structure during setup and further use it on the hot path.

Note that preemption is no longer disabled while trying to enqueue an
FD. Thus it might be possible to run the enqueue on a different CPU
(due to migration, when in process context), however this wouldn't be a
functionality issue.
Since we allow for all cores to enqueue, we take care of data
structures setup to handle the case when number of (Rx, Tx) queue pairs
is smaller than number of cores.
Signed-off-by: Horia Geantă <horia.geanta@nxp.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>