dpif-netdev: Fix comments for dp_netdev_pmd_thread struct.

dpif-netdev: Fix comments for dp_netdev_pmd_thread struct.

The sorted subtable ranking patch introduced a classifier instance per
ingress port with its subtables ranked on the frequency of hits. The PMD
thread can have more classifier instances now and solely depends on the
number of ingress ports currently handled by the pmd thread.

Fixes: 3453b4d62a98 ("dpif-netdev: dpcls per in_port with sorted subtables")
Signed-off-by: Bhanuprakash Bodireddy <bhanuprakash.bodireddy@intel.com>
Acked-by: Kevin Traynor <ktraynor@redhat.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>