dpif-netdev: Add log for PMD auto load balance interval parameter.

dpif-netdev: Add log for PMD auto load balance interval parameter.

Previously if the parameter for the PMD auto load balance minimum
interval was changed at runtime, it was not logged unless the
PMD auto load balance feature was also changed to enabled.

Log the parameter anytime it changes, and use minutes when it is
logged as that is the user input format.

Fixes: 5bf84282482a ("Adding support for PMD auto load balancing")
Signed-off-by: Kevin Traynor <ktraynor@redhat.com>
Acked-by: David Marchand <david.marchand@redhat.com>
Acked-by: Ian Stokes <ian.stokes@intel.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>